Replaced all calls to fragmentPosition() with sk_FragCoord

Change-Id: I2ed4558aea74b3ae7ee11dfe4736cdbcb16ae49e
Reviewed-on: https://skia-review.googlesource.com/8278
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/tests/ImageStorageTest.cpp b/tests/ImageStorageTest.cpp
index 20c9713..aa34831 100644
--- a/tests/ImageStorageTest.cpp
+++ b/tests/ImageStorageTest.cpp
@@ -31,7 +31,6 @@
                 : INHERITED(kNone_OptimizationFlags)
                 , fImageStorageAccess(std::move(texture), kRead_GrIOType, mm, restrict) {
             this->initClassID<TestFP>();
-            this->setWillReadFragmentPosition();
             this->addImageStorageAccess(&fImageStorageAccess);
         }
 
@@ -51,8 +50,7 @@
                     const TestFP& tfp = args.fFp.cast<TestFP>();
                     GrGLSLFPFragmentBuilder* fb = args.fFragBuilder;
                     SkString imageLoadStr;
-                    fb->codeAppendf("highp vec2 coord = %s.xy;",
-                                    args.fFragBuilder->fragmentPosition());
+                    fb->codeAppend("highp vec2 coord = sk_FragCoord.xy;");
                     fb->appendImageStorageLoad(&imageLoadStr, args.fImageStorages[0],
                                                "ivec2(coord)");
                     if (GrPixelConfigIsSint(tfp.fImageStorageAccess.texture()->config())) {