Implement hidpi and pinch-zoom scaling of filter params in cc.

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 89b1e00554a01a3e2eed1ac300305bae578e7be0..30cfce7e230fa4766661d47d1acd74477efcb5cf 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -489,6 +489,7 @@ void GLRenderer::DrawDebugBorderQuad(const DrawingFrame* frame,
 static SkBitmap ApplyImageFilter(GLRenderer* renderer,
                                  ContextProvider* offscreen_contexts,
                                  const gfx::Point& origin,
+                                 const gfx::Vector2dF& scale,
                                  SkImageFilter* filter,
                                  ScopedResource* source_texture_resource) {
   if (!filter)
@@ -552,10 +553,8 @@ static SkBitmap ApplyImageFilter(GLRenderer* renderer,
   paint.setImageFilter(filter);
   canvas.clear(SK_ColorTRANSPARENT);
 
-  // TODO(senorblanco): in addition to the origin translation here, the canvas
-  // should also be scaled to accomodate device pixel ratio and pinch zoom. See
-  // crbug.com/281516 and crbug.com/281518.
   canvas.translate(SkIntToScalar(-origin.x()), SkIntToScalar(-origin.y()));
+  canvas.scale(scale.x(), scale.y());
   canvas.drawSprite(source, 0, 0, &paint);
 
   // Flush skia context so that all the rendered stuff appears on the
@@ -767,6 +766,7 @@ scoped_ptr<ScopedResource> GLRenderer::GetBackgroundWithFilters(
         ApplyImageFilter(this,
                          frame->offscreen_context_provider,
                          quad->rect.origin(),
+                         quad->filters_scale,
                          filter.get(),
                          device_background_texture.get());
   }
@@ -901,6 +901,7 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
         filter_bitmap = ApplyImageFilter(this,
                                          frame->offscreen_context_provider,
                                          quad->rect.origin(),
+                                         quad->filters_scale,
                                          filter.get(),
                                          contents_texture);
       }