gpu: Mailbox emulation with EGLImage

ui/gl/gl_image.h

Index: ui/gl/gl_image.h
diff --git a/ui/gl/gl_image.h b/ui/gl/gl_image.h
index 08d2be60a5adfe51d5b9a4ff0144498fce6d66f9..c1358683c0624757382bc5387f755516b1de566e 100644
--- a/ui/gl/gl_image.h
+++ b/ui/gl/gl_image.h
@@ -39,6 +39,12 @@ class GL_EXPORT GLImage : public base::RefCounted<GLImage> {
   // Called after the texture has been used for drawing.
   virtual void DidUseTexImage();
 
+  // Called before the texture image data will be modified.
+  virtual void WillModifyTexImage();
+
+  // Called after the texture image data has been modified.
+  virtual void DidModifyTexImage();
+
   // Indicate that image should be released after use.
   // (For an Android work-around only).
   virtual void SetReleaseAfterUse();