Add blend constant color and use it for lcd text common case (no fancy blend or shaded text)

Review URL: http://codereview.appspot.com/4274057/

git-svn-id: http://skia.googlecode.com/svn/trunk@941 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/GrGLInterface.cpp b/gpu/src/GrGLInterface.cpp
index f296be7..fa6aa92 100644
--- a/gpu/src/GrGLInterface.cpp
+++ b/gpu/src/GrGLInterface.cpp
@@ -281,6 +281,7 @@
     GR_GL_GET_PROC(BindAttribLocation);
     GR_GL_GET_PROC(BindBuffer);
     GR_GL_GET_PROC(BindTexture);
+    GR_GL_GET_PROC(BlendColor);
     GR_GL_GET_PROC(BufferData);
     GR_GL_GET_PROC(BufferSubData);
     GR_GL_GET_PROC(CompileShader);