Make GrGLShaderBuilder::TextureSampler extract only required info from GrTextureAccess.

This will make it possible to init a TextureSampler without a texture or a specific config.

Also unify two separate bitfields of color components in GPU code.
Review URL: https://codereview.chromium.org/13121002

git-svn-id: http://skia.googlecode.com/svn/trunk@8428 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index d3b2fd4..684355d 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -866,8 +866,8 @@
 }
 
 void GrGradientEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
-    if (fIsOpaque && (kA_ValidComponentFlag & *validFlags) && 0xff == GrColorUnpackA(*color)) {
-        *validFlags = kA_ValidComponentFlag;
+    if (fIsOpaque && (kA_GrColorComponentFlag & *validFlags) && 0xff == GrColorUnpackA(*color)) {
+        *validFlags = kA_GrColorComponentFlag;
     } else {
         *validFlags = 0;
     }