Bug 1270310 - Part 3: Make string assignment in HTMLInputElement::GetValueInternal fallible. r=peterv

This makes the string assignment fallible and also adds checks for the return
value from GetValueInternal and GetValue.

dom/html/HTMLInputElement.cpp

@@ -1527,7 +1527,10 @@ HTMLInputElement::SetWidth(uint32_t aWidth)
 NS_IMETHODIMP
 HTMLInputElement::GetValue(nsAString& aValue)
 {
-  GetValueInternal(aValue);
+  nsresult rv = GetValueInternal(aValue);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
 
   // Don't return non-sanitized value for types that are experimental on mobile.
   if (IsExperimentalMobileType(mType)) {
@@ -1544,8 +1547,8 @@ HTMLInputElement::GetValueInternal(nsAString& aValue) const
     case VALUE_MODE_VALUE:
       if (IsSingleLineTextControl(false)) {
         mInputData.mState->GetValue(aValue, true);
-      } else {
-        aValue.Assign(mInputData.mValue);
+      } else if (!aValue.Assign(mInputData.mValue, fallible)) {
+        return NS_ERROR_OUT_OF_MEMORY;
       }
       return NS_OK;
 
@@ -1681,6 +1684,15 @@ HTMLInputElement::GetValueAsDecimal() const
                                                            : decimalValue;
 }
 
+void
+HTMLInputElement::GetValue(nsAString& aValue, ErrorResult& aRv)
+{
+  nsresult rv = GetValue(aValue);
+  if (NS_FAILED(rv)) {
+    aRv.Throw(rv);
+  }
+}
+
 void
 HTMLInputElement::SetValue(const nsAString& aValue, ErrorResult& aRv)
 {
@@ -5763,9 +5775,12 @@ HTMLInputElement::SaveState()
 
       inputState = new HTMLInputElementState();
       nsAutoString value;
-      GetValue(value);
-      nsresult rv =
-        nsLinebreakConverter::ConvertStringLineBreaks(
+      nsresult rv = GetValue(value);
+      if (NS_FAILED(rv)) {
+        return rv;
+      }
+
+      rv = nsLinebreakConverter::ConvertStringLineBreaks(
              value,
              nsLinebreakConverter::eLinebreakPlatform,
              nsLinebreakConverter::eLinebreakContent);