blink canvas: some cosmetic cleanups

This CL does a bit of cleanup I found around while reading the code:
- Forward-declares CanvasDrawListener.
- Reduces a verbose comment.
- Removes _ from a few internal class names (they landed like this
 in crrev.com/c/728340 but usually Chrome derived classes don't
 use _.
- Uses early-break in CanvasResourceProvider::Create() to avoid deep
 indents and use {} for if statements with large conditionals.

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ib1faf4a2d334e0a9b108c9fa02ebfbeffa0ea8c3
Reviewed-on: https://chromium-review.googlesource.com/1042905Reviewed-by: Justin Novosad <junov@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556070}

third_party/blink/renderer/core/html/canvas/canvas_rendering_context.h

@@ -63,11 +63,8 @@ class CORE_EXPORT CanvasRenderingContext : public ScriptWrappable,
  public:
   ~CanvasRenderingContext() override = default;
 
-  // A Canvas can either be "2D" or "webgl" but never both. If you request a 2D
-  // canvas and the existing context is already 2D, just return that. If the
-  // existing context is WebGL, then destroy it before creating a new 2D
-  // context. Vice versa when requesting a WebGL canvas. Requesting a context
-  // with any other type string will destroy any existing context.
+  // A Canvas can either be "2D" or "webgl" but never both. Requesting a context
+  // with a type different from an existing will destroy the latter.
   enum ContextType {
     // Do not change assigned numbers of existing items: add new features to the
     // end of the list.

third_party/blink/renderer/core/html/canvas/html_canvas_element.cc

@@ -52,6 +52,7 @@
 #include "third_party/blink/renderer/core/frame/use_counter.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_async_blob_creator.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_context_creation_attributes_core.h"
+#include "third_party/blink/renderer/core/html/canvas/canvas_draw_listener.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_font_cache.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_rendering_context.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_rendering_context_factory.h"

third_party/blink/renderer/core/html/canvas/html_canvas_element.h

@@ -37,7 +37,6 @@
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/dom/context_lifecycle_observer.h"
 #include "third_party/blink/renderer/core/dom/document.h"
-#include "third_party/blink/renderer/core/html/canvas/canvas_draw_listener.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_image_source.h"
 #include "third_party/blink/renderer/core/html/canvas/canvas_rendering_context_host.h"
 #include "third_party/blink/renderer/core/html/html_element.h"
@@ -62,6 +61,7 @@ namespace blink {
 class Canvas2DLayerBridge;
 class CanvasColorParams;
 class CanvasContextCreationAttributesCore;
+class CanvasDrawListener;
 class CanvasRenderingContext;
 class CanvasRenderingContextFactory;
 class GraphicsContext;

third_party/blink/renderer/platform/graphics/canvas_resource_provider.cc

@@ -22,15 +22,15 @@
 
 namespace blink {
 
-// CanvasResourceProvider_Texture
+// CanvasResourceProviderTexture
 //==============================================================================
 //
 // * Renders to a texture managed by skia. Mailboxes are straight GL textures.
 // * Layers are not overlay candidates
 
-class CanvasResourceProvider_Texture : public CanvasResourceProvider {
+class CanvasResourceProviderTexture : public CanvasResourceProvider {
  public:
-  CanvasResourceProvider_Texture(
+  CanvasResourceProviderTexture(
       const IntSize& size,
       unsigned msaa_sample_count,
       const CanvasColorParams color_params,
@@ -41,7 +41,7 @@ class CanvasResourceProvider_Texture : public CanvasResourceProvider {
                                std::move(context_provider_wrapper)),
         msaa_sample_count_(msaa_sample_count) {}
 
-  ~CanvasResourceProvider_Texture() override = default;
+  ~CanvasResourceProviderTexture() override = default;
 
   bool IsValid() const final { return GetSkSurface() && !IsGpuContextLost(); }
   bool IsAccelerated() const final { return true; }
@@ -118,28 +118,28 @@ class CanvasResourceProvider_Texture : public CanvasResourceProvider {
   unsigned msaa_sample_count_;
 };
 
-// CanvasResourceProvider_Texture_GpuMemoryBuffer
+// CanvasResourceProviderTextureGpuMemoryBuffer
 //==============================================================================
 //
 // * Renders to a texture managed by skia. Mailboxes are
 //     gpu-accelerated platform native surfaces.
 // * Layers are overlay candidates
 
-class CanvasResourceProvider_Texture_GpuMemoryBuffer final
-    : public CanvasResourceProvider_Texture {
+class CanvasResourceProviderTextureGpuMemoryBuffer final
+    : public CanvasResourceProviderTexture {
  public:
-  CanvasResourceProvider_Texture_GpuMemoryBuffer(
+  CanvasResourceProviderTextureGpuMemoryBuffer(
       const IntSize& size,
       unsigned msaa_sample_count,
       const CanvasColorParams color_params,
       base::WeakPtr<WebGraphicsContext3DProviderWrapper>
           context_provider_wrapper)
-      : CanvasResourceProvider_Texture(size,
-                                       msaa_sample_count,
-                                       color_params,
-                                       std::move(context_provider_wrapper)) {}
+      : CanvasResourceProviderTexture(size,
+                                      msaa_sample_count,
+                                      color_params,
+                                      std::move(context_provider_wrapper)) {}
 
-  ~CanvasResourceProvider_Texture_GpuMemoryBuffer() override = default;
+  ~CanvasResourceProviderTextureGpuMemoryBuffer() override = default;
 
  protected:
   scoped_refptr<CanvasResource> CreateResource() final {
@@ -157,7 +157,7 @@ class CanvasResourceProvider_Texture_GpuMemoryBuffer final
     scoped_refptr<CanvasResource> output_resource = NewOrRecycledResource();
     if (!output_resource) {
       // GpuMemoryBuffer creation failed, fallback to Texture resource
-      return CanvasResourceProvider_Texture::ProduceFrame();
+      return CanvasResourceProviderTexture::ProduceFrame();
     }
 
     sk_sp<SkImage> image = GetSkSurface()->makeImageSnapshot();
@@ -181,21 +181,21 @@ class CanvasResourceProvider_Texture_GpuMemoryBuffer final
   }
 };
 
-// CanvasResourceProvider_Bitmap
+// CanvasResourceProviderBitmap
 //==============================================================================
 //
 // * Renders to a skia RAM-backed bitmap
 // * Mailboxing is not supported : cannot be directly composited
 
-class CanvasResourceProvider_Bitmap final : public CanvasResourceProvider {
+class CanvasResourceProviderBitmap final : public CanvasResourceProvider {
  public:
-  CanvasResourceProvider_Bitmap(const IntSize& size,
-                                const CanvasColorParams color_params)
+  CanvasResourceProviderBitmap(const IntSize& size,
+                               const CanvasColorParams color_params)
       : CanvasResourceProvider(size,
                                color_params,
                                nullptr /*context_provider_wrapper*/) {}
 
-  ~CanvasResourceProvider_Bitmap() override = default;
+  ~CanvasResourceProviderBitmap() override = default;
 
   bool IsValid() const final { return GetSkSurface(); }
   bool IsAccelerated() const final { return false; }
@@ -275,35 +275,37 @@ std::unique_ptr<CanvasResourceProvider> CanvasResourceProvider::Create(
     switch (resource_type_fallback_list[i]) {
       case kTextureGpuMemoryBufferResourceType:
         DCHECK(SharedGpuContext::IsGpuCompositingEnabled());
-        if (RuntimeEnabledFeatures::Canvas2dImageChromiumEnabled()) {
-          if (!gpu::IsImageFromGpuMemoryBufferFormatSupported(
-                  colorParams.GetBufferFormat(),
-                  context_provider_wrapper->ContextProvider()
-                      ->GetCapabilities()))
-            continue;
-          if (!gpu::IsImageSizeValidForGpuMemoryBufferFormat(
-                  gfx::Size(size), colorParams.GetBufferFormat()))
-            continue;
-          DCHECK(gpu::IsImageFormatCompatibleWithGpuMemoryBufferFormat(
-              colorParams.GLInternalFormat(), colorParams.GetBufferFormat()));
-
-          provider =
-              std::make_unique<CanvasResourceProvider_Texture_GpuMemoryBuffer>(
-                  size, msaa_sample_count, colorParams,
-                  context_provider_wrapper);
+        if (!RuntimeEnabledFeatures::Canvas2dImageChromiumEnabled())
+          break;
+
+        if (!gpu::IsImageFromGpuMemoryBufferFormatSupported(
+                colorParams.GetBufferFormat(),
+                context_provider_wrapper->ContextProvider()
+                    ->GetCapabilities())) {
+          continue;
         }
+        if (!gpu::IsImageSizeValidForGpuMemoryBufferFormat(
+                gfx::Size(size), colorParams.GetBufferFormat())) {
+          continue;
+        }
+        DCHECK(gpu::IsImageFormatCompatibleWithGpuMemoryBufferFormat(
+            colorParams.GLInternalFormat(), colorParams.GetBufferFormat()));
+
+        provider =
+            std::make_unique<CanvasResourceProviderTextureGpuMemoryBuffer>(
+                size, msaa_sample_count, colorParams, context_provider_wrapper);
         break;
       case kTextureResourceType:
-        // TODO(xlai): Check gpu acclereration mode before using this Resource
-        // Type of CanvasResourceProvider and then Add
+        // TODO(xlai): Check gpu acceleration mode before using this Resource
+        // Type of CanvasResourceProvider and then add
         // "DCHECK(SharedGpuContext::IsGpuCompositingEnabled());" here.
-        // See crbug.com/802053.
-        provider = std::make_unique<CanvasResourceProvider_Texture>(
+        // See https://crbug.com/802053.
+        provider = std::make_unique<CanvasResourceProviderTexture>(
             size, msaa_sample_count, colorParams, context_provider_wrapper);
         break;
       case kBitmapResourceType:
         provider =
-            std::make_unique<CanvasResourceProvider_Bitmap>(size, colorParams);
+            std::make_unique<CanvasResourceProviderBitmap>(size, colorParams);
         break;
     }
     if (provider && provider->IsValid())