Replace targetHasUnifiedMultisampling in GrPB constructor

Replaces targetHasUnifiedMultisampling with a simpler "useHWAA". Now
the code that creates a pipeline builder needs to decide on its own
whether it should enable multisampling, rather than relying on the
builder to try and guess.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2041283002

Review-Url: https://codereview.chromium.org/2041283002
diff --git a/src/gpu/GrPipelineBuilder.h b/src/gpu/GrPipelineBuilder.h
index 68e70ac..cccbc2c 100644
--- a/src/gpu/GrPipelineBuilder.h
+++ b/src/gpu/GrPipelineBuilder.h
@@ -36,7 +36,7 @@
      * no GrPaint equivalents are set to default values with the exception of vertex attribute state
      * which is unmodified by this function and clipping which will be enabled.
      */
-    GrPipelineBuilder(const GrPaint&, bool targetHasUnifiedMultisampling);
+    GrPipelineBuilder(const GrPaint&, bool useHWAA = false);
 
     virtual ~GrPipelineBuilder();