Expose GpuMemoryBufferId through glGetImageivCHROMIUM.

third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h

Index: third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h
diff --git a/third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h b/third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h
index e91d658174720388eddfed0913b0f22bff8b823d..ea9fac95f94649a224a41059b3774c35203f7cc1 100644
--- a/third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h
+++ b/third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.h
@@ -156,7 +156,7 @@ private:
     // All information associated with a CHROMIUM image.
     struct ImageInfo {
         ImageInfo() {}
-        ImageInfo(GLuint imageId, GLuint textureId);
+        ImageInfo(GLuint imageId, GLuint textureId, GLint gpuMemoryBufferId);
 
         // Whether this structure holds references to a CHROMIUM image.
         bool empty();
@@ -166,6 +166,9 @@ private:
 
         // The id of the texture bound to the CHROMIUM image.
         GLuint m_textureId = 0;
+
+        // The id of the GpuMemoryBuffer backing the texture and CHROMIUM image.
+        GLint m_gpuMemoryBufferId = -1;
     };
 #endif // USE_IOSURFACE_FOR_2D_CANVAS