Add GL_CHROMIUM_map_sub functions to GrGLInterface and bit to GrGLCaps.

src/gpu/gl/GrGLCaps.h

Index: src/gpu/gl/GrGLCaps.h
diff --git a/src/gpu/gl/GrGLCaps.h b/src/gpu/gl/GrGLCaps.h
index 4cde2bd5f7317b8902a4a68e9ae6ac3f1991293e..1ba21ec72fccb208d4abdd69ab5bbe9f0dd5b5a1 100644
--- a/src/gpu/gl/GrGLCaps.h
+++ b/src/gpu/gl/GrGLCaps.h
@@ -259,6 +259,9 @@ public:
 
     bool dropsTileOnZeroDivide() const { return fDropsTileOnZeroDivide; }
 
+    /// Is GL_CHROMIUM_map_sub supported?
+    bool mapSubSupport() const { return fMapSubSupport; }
+
 private:
     /**
      * Maintains a bit per GrPixelConfig. It is used to avoid redundantly
@@ -341,6 +344,7 @@ private:
     bool fFixedFunctionSupport : 1;
     bool fFullClearIsFree : 1;
     bool fDropsTileOnZeroDivide : 1;
+    bool fMapSubSupport : 1;
 
     typedef GrDrawTargetCaps INHERITED;
 };