Rename kES2_GrGLBinding to kES_GrGLBinding. Step 0 for supporting ES3.

R=robertphillips@google.com

Review URL: https://codereview.chromium.org/23185004

git-svn-id: http://skia.googlecode.com/svn/trunk@10747 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/GrGLShaderVar.h b/src/gpu/gl/GrGLShaderVar.h
index e03ed3e..0123b38 100644
--- a/src/gpu/gl/GrGLShaderVar.h
+++ b/src/gpu/gl/GrGLShaderVar.h
@@ -304,7 +304,7 @@
 
     static const char* PrecisionString(Precision p, GrGLBinding binding) {
         // Desktop GLSL has added precision qualifiers but they don't do anything.
-        if (kES2_GrGLBinding == binding) {
+        if (kES_GrGLBinding == binding) {
             switch (p) {
                 case kLow_Precision:
                     return "lowp ";