WebGL: Tidy up buffer allocation logic

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 275 matching lines @@
     bool texture_binding_dirty_ = false;
     bool renderbuffer_binding_dirty_ = false;
     bool framebuffer_binding_dirty_ = false;
     bool pixel_unpack_buffer_binding_dirty_ = false;
   };
 
   // All parameters necessary to generate the texture for the ColorBuffer.
   struct ColorBufferParameters {
     DISALLOW_NEW();
     GLenum target = 0;
-    GLenum internal_color_format = 0;
-
-    // The internal color format used when allocating storage for the
-    // texture. This may be different from internalColorFormat if RGB
-    // emulation is required.
-    GLenum creation_internal_color_format = 0;
-    GLenum color_format = 0;
+    bool allocate_alpha_channel = false;
   };
 
   struct ColorBuffer : public RefCounted<ColorBuffer> {
     ColorBuffer(DrawingBuffer*,
                 const ColorBufferParameters&,
                 const IntSize&,
                 GLuint texture_id,
                 GLuint image_id,
                 std::unique_ptr<gfx::GpuMemoryBuffer>);
     ~ColorBuffer();
@@ skipping 218 matching lines @@
   // RuntimeEnabledFeatures::webGLImageChromiumEnabled() call with
   // shouldUseChromiumImage() calls, and set m_chromiumImageUsage to
   // DisallowChromiumImage in the case of OffscreenCanvas.
   ChromiumImageUsage chromium_image_usage_;
   bool ShouldUseChromiumImage();
 };
 
 }  // namespace blink
 
 #endif  // DrawingBuffer_h