diff --git a/content/canvas/compiledtest/TestWebGLElementArrayCache.cpp b/content/canvas/compiledtest/TestWebGLElementArrayCache.cpp
index 5fa4a701dc63..b5f05ea58b03 100644
--- a/content/canvas/compiledtest/TestWebGLElementArrayCache.cpp
+++ b/content/canvas/compiledtest/TestWebGLElementArrayCache.cpp
@@ -48,9 +48,15 @@ T RandomInteger(T a, T b)
 template<typename T>
 GLenum GLType()
 {
-  return sizeof(T) == 1
-             ? LOCAL_GL_UNSIGNED_BYTE
-             : LOCAL_GL_UNSIGNED_SHORT;
+  switch (sizeof(T))
+  {
+    case 4:  return LOCAL_GL_UNSIGNED_INT;
+    case 2:  return LOCAL_GL_UNSIGNED_SHORT;
+    case 1:  return LOCAL_GL_UNSIGNED_BYTE;
+    default:
+      VERIFY(false);
+      return 0;
+  }
 }
 
 template<typename T>
@@ -79,6 +85,7 @@ void CheckValidate(WebGLElementArrayCache& c, size_t firstByte, size_t countByte
 {
   CheckValidateOneType<uint8_t>(c, firstByte, countBytes);
   CheckValidateOneType<uint16_t>(c, firstByte, countBytes);
+  CheckValidateOneType<uint32_t>(c, firstByte, countBytes);
 }
 
 template<typename T>
@@ -151,6 +158,7 @@ int main(int argc, char *argv[])
 
   CheckSanity<uint8_t>();
   CheckSanity<uint16_t>();
+  CheckSanity<uint32_t>();
 
   CheckUintOverflow<uint8_t>();
   CheckUintOverflow<uint16_t>();
diff --git a/content/canvas/src/Makefile.in b/content/canvas/src/Makefile.in
index 76095e93f10e..47cff6df562e 100644
--- a/content/canvas/src/Makefile.in
+++ b/content/canvas/src/Makefile.in
@@ -40,6 +40,7 @@ CPPSRCS += \
 	WebGLExtensionCompressedTextureS3TC.cpp \
 	WebGLExtensionDebugRendererInfo.cpp \
 	WebGLExtensionDepthTexture.cpp \
+	WebGLExtensionElementIndexUint.cpp \
 	WebGLExtensionLoseContext.cpp \
 	WebGLExtensionStandardDerivatives.cpp \
 	WebGLExtensionTextureFilterAnisotropic.cpp \
diff --git a/content/canvas/src/WebGLContext.cpp b/content/canvas/src/WebGLContext.cpp
index 907853921f2c..611906fed097 100644
--- a/content/canvas/src/WebGLContext.cpp
+++ b/content/canvas/src/WebGLContext.cpp
@@ -943,6 +943,8 @@ bool WebGLContext::IsExtensionSupported(JSContext *cx, WebGLExtensionID ext) con
     }
 
     switch (ext) {
+        case OES_element_index_uint:
+            return !gl->IsGLES2() || gl->IsExtensionSupported(GLContext::OES_element_index_uint);
         case OES_standard_derivatives:
         case WEBGL_lose_context:
             // We always support these extensions.
@@ -1013,7 +1015,11 @@ WebGLContext::GetExtension(JSContext *cx, const nsAString& aName, ErrorResult& r
     WebGLExtensionID ext = WebGLExtensionID_unknown_extension;
 
     // step 1: figure what extension is wanted
-    if (CompareWebGLExtensionName(name, "OES_texture_float"))
+    if (CompareWebGLExtensionName(name, "OES_element_index_uint"))
+    {
+        ext = OES_element_index_uint;
+    }
+    else if (CompareWebGLExtensionName(name, "OES_texture_float"))
     {
         ext = OES_texture_float;
     }
@@ -1075,6 +1081,9 @@ WebGLContext::GetExtension(JSContext *cx, const nsAString& aName, ErrorResult& r
     if (!IsExtensionEnabled(ext)) {
         WebGLExtensionBase *obj = nullptr;
         switch (ext) {
+            case OES_element_index_uint:
+                obj = new WebGLExtensionElementIndexUint(this);
+                break;
             case OES_standard_derivatives:
                 obj = new WebGLExtensionStandardDerivatives(this);
                 break;
@@ -1439,6 +1448,8 @@ WebGLContext::GetSupportedExtensions(JSContext *cx, Nullable< nsTArray<nsString>
 
     nsTArray<nsString>& arr = retval.SetValue();
 
+    if (IsExtensionSupported(cx, OES_element_index_uint))
+        arr.AppendElement(NS_LITERAL_STRING("OES_element_index_uint"));
     if (IsExtensionSupported(cx, OES_texture_float))
         arr.AppendElement(NS_LITERAL_STRING("OES_texture_float"));
     if (IsExtensionSupported(cx, OES_standard_derivatives))
diff --git a/content/canvas/src/WebGLContext.h b/content/canvas/src/WebGLContext.h
index 5c9d09c01089..5ffc98c2a598 100644
--- a/content/canvas/src/WebGLContext.h
+++ b/content/canvas/src/WebGLContext.h
@@ -912,6 +912,7 @@ protected:
     // extensions
     enum WebGLExtensionID {
         EXT_texture_filter_anisotropic,
+        OES_element_index_uint,
         OES_standard_derivatives,
         OES_texture_float,
         WEBGL_compressed_texture_atc,
diff --git a/content/canvas/src/WebGLContextGL.cpp b/content/canvas/src/WebGLContextGL.cpp
index 508ee6abed30..4940f12a26c4 100644
--- a/content/canvas/src/WebGLContextGL.cpp
+++ b/content/canvas/src/WebGLContextGL.cpp
@@ -1511,6 +1511,11 @@ WebGLContext::DrawElements(WebGLenum mode, WebGLsizei count, WebGLenum type,
     } else if (type == LOCAL_GL_UNSIGNED_BYTE) {
         checked_byteCount = count;
         first = byteOffset;
+    } else if (type == LOCAL_GL_UNSIGNED_INT && IsExtensionEnabled(OES_element_index_uint)) {
+        checked_byteCount = 4 * CheckedUint32(count);
+        if (byteOffset % 4 != 0)
+            return ErrorInvalidOperation("drawElements: invalid byteOffset for UNSIGNED_INT (must be a multiple of 4)");
+        first = byteOffset / 4;
     } else {
         return ErrorInvalidEnum("drawElements: type must be UNSIGNED_SHORT or UNSIGNED_BYTE");
     }
diff --git a/content/canvas/src/WebGLElementArrayCache.cpp b/content/canvas/src/WebGLElementArrayCache.cpp
index 791640e8cdf4..5780935500b8 100644
--- a/content/canvas/src/WebGLElementArrayCache.cpp
+++ b/content/canvas/src/WebGLElementArrayCache.cpp
@@ -106,8 +106,8 @@ namespace mozilla {
  * by having WebGLElementArrayCache lazily create trees for each type only upon first use.
  *
  * Another consequence of this constraint is that when invalidating the trees, we have to invalidate
- * all existing trees. So if trees for types uint8_t and uint16_t have ever been constructed for this buffer,
- * every subsequent invalidation will have to invalidate both trees even if one of the two types is never
+ * all existing trees. So if trees for types uint8_t, uint16_t and uint32_t have ever been constructed for this buffer,
+ * every subsequent invalidation will have to invalidate all trees even if one of the types is never
  * used again. This implies that it is important to minimize the cost of invalidation i.e.
  * do lazy updates upon use as opposed to immediately updating invalidated trees. This poses a problem:
  * it is nontrivial to keep track of the part of the tree that's invalidated. The current solution
@@ -329,6 +329,12 @@ struct TreeForType<uint16_t>
   static WebGLElementArrayCacheTree<uint16_t>*& Run(WebGLElementArrayCache *b) { return b->mUint16Tree; }
 };
 
+template<>
+struct TreeForType<uint32_t>
+{
+  static WebGLElementArrayCacheTree<uint32_t>*& Run(WebGLElementArrayCache *b) { return b->mUint32Tree; }
+};
+
 // When the buffer gets updated from firstByte to lastByte,
 // calling this method will notify the tree accordingly
 template<typename T>
@@ -441,6 +447,7 @@ void WebGLElementArrayCacheTree<T>::Update()
 WebGLElementArrayCache::~WebGLElementArrayCache() {
   delete mUint8Tree;
   delete mUint16Tree;
+  delete mUint32Tree;
   free(mUntypedData);
 }
 
@@ -452,6 +459,9 @@ bool WebGLElementArrayCache::BufferData(const void* ptr, size_t byteSize) {
   if (mUint16Tree)
     if (!mUint16Tree->ResizeToParentSize())
       return false;
+  if (mUint32Tree)
+    if (!mUint32Tree->ResizeToParentSize())
+      return false;
   mUntypedData = realloc(mUntypedData, byteSize);
   if (!mUntypedData)
     return false;
@@ -474,6 +484,8 @@ void WebGLElementArrayCache::InvalidateTrees(size_t firstByte, size_t lastByte)
     mUint8Tree->Invalidate(firstByte, lastByte);
   if (mUint16Tree)
     mUint16Tree->Invalidate(firstByte, lastByte);
+  if (mUint32Tree)
+    mUint32Tree->Invalidate(firstByte, lastByte);
 }
 
 template<typename T>
@@ -541,16 +553,20 @@ bool WebGLElementArrayCache::Validate(GLenum type, uint32_t maxAllowed, size_t f
     return Validate<uint8_t>(maxAllowed, firstElement, countElements);
   if (type == LOCAL_GL_UNSIGNED_SHORT)
     return Validate<uint16_t>(maxAllowed, firstElement, countElements);
+  if (type == LOCAL_GL_UNSIGNED_INT)
+    return Validate<uint32_t>(maxAllowed, firstElement, countElements);
   return false;
 }
 
 size_t WebGLElementArrayCache::SizeOfIncludingThis(nsMallocSizeOfFun aMallocSizeOf) const {
   size_t uint8TreeSize  = mUint8Tree  ? mUint8Tree->SizeOfIncludingThis(aMallocSizeOf) : 0;
   size_t uint16TreeSize = mUint16Tree ? mUint16Tree->SizeOfIncludingThis(aMallocSizeOf) : 0;
+  size_t uint32TreeSize = mUint32Tree ? mUint32Tree->SizeOfIncludingThis(aMallocSizeOf) : 0;
   return aMallocSizeOf(this) +
           mByteSize +
           uint8TreeSize +
-          uint16TreeSize;
+          uint16TreeSize +
+          uint32TreeSize;
 }
 
 } // end namespace mozilla
diff --git a/content/canvas/src/WebGLElementArrayCache.h b/content/canvas/src/WebGLElementArrayCache.h
index 3646f60cf2e5..68d1f582ea64 100644
--- a/content/canvas/src/WebGLElementArrayCache.h
+++ b/content/canvas/src/WebGLElementArrayCache.h
@@ -42,6 +42,7 @@ public:
     , mByteSize(0)
     , mUint8Tree(nullptr)
     , mUint16Tree(nullptr)
+    , mUint32Tree(nullptr)
   {}
 
   ~WebGLElementArrayCache();
@@ -73,6 +74,7 @@ private:
   size_t mByteSize;
   WebGLElementArrayCacheTree<uint8_t>* mUint8Tree;
   WebGLElementArrayCacheTree<uint16_t>* mUint16Tree;
+  WebGLElementArrayCacheTree<uint32_t>* mUint32Tree;
 };
 
 
diff --git a/content/canvas/src/WebGLExtensionElementIndexUint.cpp b/content/canvas/src/WebGLExtensionElementIndexUint.cpp
new file mode 100644
index 000000000000..49ab44527e3a
--- /dev/null
+++ b/content/canvas/src/WebGLExtensionElementIndexUint.cpp
@@ -0,0 +1,21 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WebGLContext.h"
+#include "WebGLExtensions.h"
+#include "mozilla/dom/WebGLRenderingContextBinding.h"
+
+using namespace mozilla;
+
+WebGLExtensionElementIndexUint::WebGLExtensionElementIndexUint(WebGLContext* context)
+    : WebGLExtensionBase(context)
+{
+}
+
+WebGLExtensionElementIndexUint::~WebGLExtensionElementIndexUint()
+{
+}
+
+IMPL_WEBGL_EXTENSION_GOOP(WebGLExtensionElementIndexUint)
diff --git a/content/canvas/src/WebGLExtensions.h b/content/canvas/src/WebGLExtensions.h
index 504295d414ee..fe7352181af1 100644
--- a/content/canvas/src/WebGLExtensions.h
+++ b/content/canvas/src/WebGLExtensions.h
@@ -87,6 +87,16 @@ public:
     DECL_WEBGL_EXTENSION_GOOP
 };
 
+class WebGLExtensionElementIndexUint
+    : public WebGLExtensionBase
+{
+public:
+    WebGLExtensionElementIndexUint(WebGLContext*);
+    virtual ~WebGLExtensionElementIndexUint();
+
+    DECL_WEBGL_EXTENSION_GOOP
+};
+
 class WebGLExtensionLoseContext
     : public WebGLExtensionBase
 {
diff --git a/dom/bindings/Bindings.conf b/dom/bindings/Bindings.conf
index a12d4e8cb3f8..e7166932708c 100644
--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -1102,6 +1102,11 @@ DOMInterfaces = {
    'headerFile': 'WebGLExtensions.h'
 },
 
+'WebGLExtensionElementIndexUint': {
+   'nativeType': 'mozilla::WebGLExtensionElementIndexUint',
+   'headerFile': 'WebGLExtensions.h'
+},
+
 'WebGLExtensionLoseContext': {
    'nativeType': 'mozilla::WebGLExtensionLoseContext',
    'headerFile': 'WebGLExtensions.h'
diff --git a/dom/webidl/WebGLRenderingContext.webidl b/dom/webidl/WebGLRenderingContext.webidl
index b458599e5d03..dffb49429b62 100644
--- a/dom/webidl/WebGLRenderingContext.webidl
+++ b/dom/webidl/WebGLRenderingContext.webidl
@@ -806,6 +806,11 @@ interface WebGLExtensionDepthTexture
     const GLenum UNSIGNED_INT_24_8_WEBGL = 0x84FA;
 };
 
+[NoInterfaceObject]
+interface WebGLExtensionElementIndexUint
+{
+};
+
 [NoInterfaceObject]
 interface WebGLExtensionLoseContext {
     void loseContext();
diff --git a/gfx/gl/GLContext.cpp b/gfx/gl/GLContext.cpp
index a74541149444..2c1aa0ce4ac6 100644
--- a/gfx/gl/GLContext.cpp
+++ b/gfx/gl/GLContext.cpp
@@ -80,6 +80,7 @@ static const char *sExtensionNames[] = {
     "GL_OES_EGL_sync",
     "GL_OES_EGL_image_external",
     "GL_EXT_packed_depth_stencil",
+    "GL_OES_element_index_uint",
     nullptr
 };
 
diff --git a/gfx/gl/GLContext.h b/gfx/gl/GLContext.h
index 303e4fdf2fde..8b11a6c10881 100644
--- a/gfx/gl/GLContext.h
+++ b/gfx/gl/GLContext.h
@@ -1016,6 +1016,7 @@ public:
         OES_EGL_sync,
         OES_EGL_image_external,
         EXT_packed_depth_stencil,
+        OES_element_index_uint,
         Extensions_Max
     };