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/GrGpuGLFixed.cpp b/gpu/src/GrGpuGLFixed.cpp
index 695b22c..afd9bb6 100644
--- a/gpu/src/GrGpuGLFixed.cpp
+++ b/gpu/src/GrGpuGLFixed.cpp
@@ -137,6 +137,14 @@
         }
     }
 
+#if GR_SUPPORT_GLES1
+    if (BlendCoefReferencesConstant(fCurrDrawState.fSrcBlend) ||
+        BlendCoefReferencesConstant(fCurrDrawState.fDstBlend)) {
+        uimpl("ES1 doesn't support blend constant");
+        return false;
+    }
+#endif
+
     if (!flushGLStateCommon(type)) {
         return false;
     }