Fix for MSAN unintialized value

BUG=524094

Review URL: https://codereview.chromium.org/1320433002
diff --git a/src/gpu/effects/GrTextureDomain.cpp b/src/gpu/effects/GrTextureDomain.cpp
index 3810c34..e5ae18c 100644
--- a/src/gpu/effects/GrTextureDomain.cpp
+++ b/src/gpu/effects/GrTextureDomain.cpp
@@ -146,7 +146,7 @@
                                         GrSurfaceOrigin textureOrigin) {
     SkASSERT(textureDomain.mode() == fMode);
     if (kIgnore_Mode != textureDomain.mode()) {
-        GrGLfloat values[4] = {
+        GrGLfloat values[kPrevDomainCount] = {
             SkScalarToFloat(textureDomain.domain().left()),
             SkScalarToFloat(textureDomain.domain().top()),
             SkScalarToFloat(textureDomain.domain().right()),
@@ -160,9 +160,9 @@
             // of elements so that values = (l, t, r, b).
             SkTSwap(values[1], values[3]);
         }
-        if (0 != memcmp(values, fPrevDomain, 4 * sizeof(GrGLfloat))) {
+        if (0 != memcmp(values, fPrevDomain, kPrevDomainCount * sizeof(GrGLfloat))) {
             pdman.set4fv(fDomainUni, 1, values);
-            memcpy(fPrevDomain, values, 4 * sizeof(GrGLfloat));
+            memcpy(fPrevDomain, values, kPrevDomainCount * sizeof(GrGLfloat));
         }
     }
 }
diff --git a/src/gpu/effects/GrTextureDomain.h b/src/gpu/effects/GrTextureDomain.h
index a2e6652..11760fb 100644
--- a/src/gpu/effects/GrTextureDomain.h
+++ b/src/gpu/effects/GrTextureDomain.h
@@ -95,7 +95,9 @@
     class GLDomain {
     public:
         GLDomain() {
-            fPrevDomain[0] = SK_FloatNaN;
+            for (int i = 0; i < kPrevDomainCount; i++) {
+                fPrevDomain[i] = SK_FloatNaN;
+            }
             SkDEBUGCODE(fMode = (Mode) -1;)
         }
 
@@ -137,10 +139,11 @@
         }
 
     private:
+        static const int kPrevDomainCount = 4;
         SkDEBUGCODE(Mode                      fMode;)
         GrGLProgramDataManager::UniformHandle fDomainUni;
         SkString                              fDomainName;
-        GrGLfloat                             fPrevDomain[4];
+        GrGLfloat                             fPrevDomain[kPrevDomainCount];
     };
 
 protected: