WebGL: Tidy up buffer allocation logic

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

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
index 938c0c3b69880e217d1d0c90543b445f44d1b3a5..56f1eea05f3abd78eada2f5db471b6905ff3b8e9 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.h
@@ -293,13 +293,7 @@ class PLATFORM_EXPORT DrawingBuffer
   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> {