Add GL_CHROMIUM_map_sub functions to GrGLInterface and bit to GrGLCaps.

BUG=skia:2402
R=robertphillips@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/231773003

git-svn-id: http://skia.googlecode.com/svn/trunk@14199 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/GrGLInterface.cpp b/src/gpu/gl/GrGLInterface.cpp
index c5ab39a..bfffdfb 100644
--- a/src/gpu/gl/GrGLInterface.cpp
+++ b/src/gpu/gl/GrGLInterface.cpp
@@ -504,6 +504,15 @@
             RETURN_FALSE_INTERFACE;
         }
     }
+
+    if (kGLES_GrGLStandard == fStandard && fExtensions.has("GL_CHROMIUM_map_sub")) {
+        if (NULL == fFunctions.fMapBufferSubData ||
+            NULL == fFunctions.fMapTexSubImage2D ||
+            NULL == fFunctions.fUnmapBufferSubData ||
+            NULL == fFunctions.fUnmapTexSubImage2D) {
+            RETURN_FALSE_INTERFACE;
+        }
+    }
 #endif
 
     return true;