fix bitmap shader leak in gm

this was introduced in https://codereview.chromium.org/245963010

this was detected by caryclark@ by examining the result of valgrind on the skia buildbots

BUG=skia:1976
R=caryclark@google.com

Author: dominikg@chromium.org

Review URL: https://codereview.chromium.org/255253002

git-svn-id: http://skia.googlecode.com/svn/trunk@14450 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/shadertext2.cpp b/gm/shadertext2.cpp
index e580d91..87fe1b2 100644
--- a/gm/shadertext2.cpp
+++ b/gm/shadertext2.cpp
@@ -154,10 +154,11 @@
                 canvas->translate(0, kPadY / 2 + kPointSize);
                 columnH += kPadY / 2 + kPointSize;
                 for (int lm = 0; lm < localMatrices.count(); ++lm) {
-                    paint.setShader(SkShader::CreateBitmapShader(bmp,
-                                                                 SkShader::kMirror_TileMode,
-                                                                 SkShader::kRepeat_TileMode,
-                                                                 &localMatrices[lm].fMatrix));
+                    paint.setShader(
+                            SkShader::CreateBitmapShader(bmp,
+                                                         SkShader::kMirror_TileMode,
+                                                         SkShader::kRepeat_TileMode,
+                                                         &localMatrices[lm].fMatrix))->unref();
 
                     canvas->save();
                         canvas->concat(matrices[m].fMatrix);