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

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

dom/html/HTMLInputElement.cpp

@@ -2015,7 +2015,10 @@ 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)) {
@@ -2032,8 +2035,8 @@ 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;
 
@@ -2169,6 +2172,15 @@ 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)
 {
@@ -6314,9 +6326,12 @@ 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);

dom/html/HTMLInputElement.h

@@ -632,7 +632,7 @@ public:
     SetHTMLAttr(nsGkAtoms::value, aValue, aRv);
   }
 
-  // XPCOM GetValue() is OK
+  void GetValue(nsAString& aValue, ErrorResult& aRv);
   void SetValue(const nsAString& aValue, ErrorResult& aRv);
 
   Nullable<Date> GetValueAsDate(ErrorResult& aRv);

dom/webidl/HTMLInputElement.webidl

@@ -86,7 +86,7 @@ interface HTMLInputElement : HTMLElement {
            attribute DOMString type;
   [Pure, SetterThrows]
            attribute DOMString defaultValue;
-  [Pure, TreatNullAs=EmptyString, SetterThrows]
+  [Pure, TreatNullAs=EmptyString, Throws]
            attribute DOMString value;
   [Throws, Pref="dom.experimental_forms"]
            attribute Date? valueAsDate;