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/batches/GrAALinearizingConvexPathRenderer.cpp b/src/gpu/batches/GrAALinearizingConvexPathRenderer.cpp
index a3e00d1..227f86b 100644
--- a/src/gpu/batches/GrAALinearizingConvexPathRenderer.cpp
+++ b/src/gpu/batches/GrAALinearizingConvexPathRenderer.cpp
@@ -322,6 +322,8 @@
 bool GrAALinearizingConvexPathRenderer::onDrawPath(const DrawPathArgs& args) {
     GR_AUDIT_TRAIL_AUTO_FRAME(args.fDrawContext->auditTrail(),
                               "GrAALinearizingConvexPathRenderer::onDrawPath");
+    SkASSERT(!args.fDrawContext->isUnifiedMultisampled());
+
     if (args.fPath->isEmpty()) {
         return true;
     }
@@ -336,7 +338,7 @@
 
     SkAutoTUnref<GrDrawBatch> batch(AAFlatteningConvexPathBatch::Create(geometry));
 
-    GrPipelineBuilder pipelineBuilder(*args.fPaint, args.fDrawContext->isUnifiedMultisampled());
+    GrPipelineBuilder pipelineBuilder(*args.fPaint);
     pipelineBuilder.setUserStencil(args.fUserStencilSettings);
 
     args.fDrawContext->drawBatch(pipelineBuilder, *args.fClip, batch);