Add GM that tests GrTextureDomain and fix bug where kDecal_Mode gets incorrectly ignored.

R=robertphillips@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/208313017

git-svn-id: http://skia.googlecode.com/svn/trunk@13933 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/effects/GrTextureDomain.cpp b/src/gpu/effects/GrTextureDomain.cpp
index 70d6159..656000b 100644
--- a/src/gpu/effects/GrTextureDomain.cpp
+++ b/src/gpu/effects/GrTextureDomain.cpp
@@ -16,7 +16,7 @@
     : fIndex(index) {
 
     static const SkRect kFullRect = {0, 0, SK_Scalar1, SK_Scalar1};
-    if (domain.contains(kFullRect)) {
+    if (domain.contains(kFullRect) && kClamp_Mode == mode) {
         fMode = kIgnore_Mode;
     } else {
         fMode = mode;