Add compositor support for half-float RGBA buffers and textures

cc/output/software_renderer.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/output/software_renderer.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/output/copy_output_request.h"
@@ skipping 47 matching lines @@
     : DirectRenderer(settings, output_surface, resource_provider),
       output_device_(output_surface->software_device()) {
 }
 
 SoftwareRenderer::~SoftwareRenderer() {}
 
 bool SoftwareRenderer::CanPartialSwap() {
   return true;
 }
 
+ResourceFormat SoftwareRenderer::BackbufferFormat() const {
+  return resource_provider_->best_texture_format();
+}
+
 void SoftwareRenderer::BeginDrawingFrame(DrawingFrame* frame) {
   TRACE_EVENT0("cc", "SoftwareRenderer::BeginDrawingFrame");
   root_canvas_ = output_device_->BeginPaint(frame->root_damage_rect);
 }
 
 void SoftwareRenderer::FinishDrawingFrame(DrawingFrame* frame) {
   TRACE_EVENT0("cc", "SoftwareRenderer::FinishDrawingFrame");
   current_framebuffer_lock_ = nullptr;
   current_framebuffer_canvas_.reset();
   current_canvas_ = nullptr;
@@ skipping 641 matching lines @@
       ApplyImageFilter(filter.get(), quad, backdrop_bitmap, nullptr);
 
   if (!filter_backdrop_image)
     return nullptr;
 
   return filter_backdrop_image->makeShader(content_tile_mode, content_tile_mode,
                                            &filter_backdrop_transform);
 }
 
 }  // namespace cc