Use high precision vertex attributes.

src/gpu/GrPrimitiveProcessor.h

Index: src/gpu/GrPrimitiveProcessor.h
diff --git a/src/gpu/GrPrimitiveProcessor.h b/src/gpu/GrPrimitiveProcessor.h
index 2e25bdbab89963945ce8a663f4f5613588f1b4e8..4147b74963aaaf988f92398f94ec6eb643262b98 100644
--- a/src/gpu/GrPrimitiveProcessor.h
+++ b/src/gpu/GrPrimitiveProcessor.h
@@ -126,13 +126,16 @@ public:
             : fName(NULL)
             , fType(kFloat_GrVertexAttribType)
             , fOffset(0) {}
-        Attribute(const char* name, GrVertexAttribType type)
+        Attribute(const char* name, GrVertexAttribType type,
+                  GrSLPrecision precision = kDefault_GrSLPrecision)
             : fName(name)
             , fType(type)
-            , fOffset(SkAlign4(GrVertexAttribTypeSize(type))) {}
+            , fOffset(SkAlign4(GrVertexAttribTypeSize(type)))
+            , fPrecision(precision) {}
         const char* fName;
         GrVertexAttribType fType;
         size_t fOffset;
+        GrSLPrecision fPrecision;
     };
 
     int numAttribs() const { return fNumAttribs; }