Bug 1287321 - Don't fire input event on type=range when value hasn't changed. r=baku

dom/html/HTMLInputElement.cpp

@@ -3902,6 +3902,8 @@ HTMLInputElement::SetValueOfRangeForUserEvent(Decimal aValue)
 {
   MOZ_ASSERT(aValue.isFinite());
 
+  Decimal oldValue = GetValueAsDecimal();
+
   nsAutoString val;
   ConvertNumberToString(aValue, val);
   // TODO: What should we do if SetValueInternal fails?  (The allocation
@@ -3912,10 +3914,13 @@ HTMLInputElement::SetValueOfRangeForUserEvent(Decimal aValue)
   if (frame) {
     frame->UpdateForValueChange();
   }
-  nsContentUtils::DispatchTrustedEvent(OwnerDoc(),
-                                       static_cast<nsIDOMHTMLInputElement*>(this),
-                                       NS_LITERAL_STRING("input"), true,
-                                       false);
+
+  if (GetValueAsDecimal() != oldValue) {
+    nsContentUtils::DispatchTrustedEvent(OwnerDoc(),
+                                         static_cast<nsIDOMHTMLInputElement*>(this),
+                                         NS_LITERAL_STRING("input"), true,
+                                         false);
+  }
 }
 
 void