Expose ImageBitmapRenderingContext to users

ImageBitmapRenderingContext is supposed to be shipped in Chrome 55 as stated
in the Chrome Platform Status here:
https://www.chromestatus.com/feature/5709799995998208. However, the code itself
bars this feature from being accessible by users.


Bug: 658734
Change-Id: I7b54bbee58529507411109866885623ef5b7a999
Reviewed-on: https://chromium-review.googlesource.com/938461Reviewed-by: Justin Novosad <junov@chromium.org>
Commit-Queue: Olivia Lai <xlai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539428}

third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp

@@ -148,8 +148,7 @@ CanvasRenderingContext::ContextType CanvasRenderingContext::ContextTypeFromId(
     return kContextWebgl;
   if (id == "webgl2")
     return kContextWebgl2;
-  if (id == "bitmaprenderer" &&
-      RuntimeEnabledFeatures::ExperimentalCanvasFeaturesEnabled()) {
+  if (id == "bitmaprenderer") {
     return kContextImageBitmap;
   }
   if (id == "xrpresent" && RuntimeEnabledFeatures::WebXREnabled()) {

third_party/WebKit/Source/modules/canvas/imagebitmap/ImageBitmapRenderingContext.cpp

@@ -37,8 +37,6 @@ void ImageBitmapRenderingContext::transferFromImageBitmap(
 CanvasRenderingContext* ImageBitmapRenderingContext::Factory::Create(
     CanvasRenderingContextHost* host,
     const CanvasContextCreationAttributesCore& attrs) {
-  if (!RuntimeEnabledFeatures::ExperimentalCanvasFeaturesEnabled())
-    return nullptr;
   return new ImageBitmapRenderingContext(host, attrs);
 }