gpu: Use a rectangle to keep track of the cleared area of each texture level.

gpu/command_buffer/service/gles2_cmd_decoder.h

Index: gpu/command_buffer/service/gles2_cmd_decoder.h
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.h b/gpu/command_buffer/service/gles2_cmd_decoder.h
index ac01c95804cc0a2dcd1d30864915d422a91e937a..36a0b20d2d6a3e52ecfb5e6a73fcb7ed25e70495 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.h
@@ -210,18 +210,17 @@ class GPU_EXPORT GLES2Decoder : public base::SupportsWeakPtr<GLES2Decoder>,
   // Provides detail about a lost context if one occurred.
   virtual error::ContextLostReason GetContextLostReason() = 0;
 
-  // Clears a level of a texture
+  // Clears a level sub area of a texture
   // Returns false if a GL error should be generated.
-  virtual bool ClearLevel(
-      Texture* texture,
-      unsigned target,
-      int level,
-      unsigned internal_format,
-      unsigned format,
-      unsigned type,
-      int width,
-      int height,
-      bool is_texture_immutable) = 0;
+  virtual bool ClearLevel(Texture* texture,
+                          unsigned target,
+                          int level,
+                          unsigned format,
+                          unsigned type,
+                          int xoffset,
+                          int yoffset,
+                          int width,
+                          int height) = 0;
 
   virtual ErrorState* GetErrorState() = 0;