Add hooks for GL_EXT_debug_marker in gpu

BUG=skia:
R=bsalomon@google.com

Author: egdaniel@google.com

Review URL: https://codereview.chromium.org/174123003

git-svn-id: http://skia.googlecode.com/svn/trunk@13538 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrInOrderDrawBuffer.h b/src/gpu/GrInOrderDrawBuffer.h
index 6b680b2..60e01f0 100644
--- a/src/gpu/GrInOrderDrawBuffer.h
+++ b/src/gpu/GrInOrderDrawBuffer.h
@@ -168,6 +168,11 @@
 
     bool quickInsideClip(const SkRect& devBounds);
 
+    virtual void onInstantGpuTraceEvent(const char* marker) SK_OVERRIDE;
+    virtual void onPushGpuTraceEvent(const char* marker) SK_OVERRIDE;
+    virtual void onPopGpuTraceEvent() SK_OVERRIDE;
+
+
     // Attempts to concat instances from info onto the previous draw. info must represent an
     // instanced draw. The caller must have already recorded a new draw state and clip if necessary.
     int concatInstancedDraw(const DrawInfo& info);