Fix dashing bug where hwaa was unintentionally disabled

src/gpu/batches/GrDashLinePathRenderer.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDashLinePathRenderer.h"
 
 #include "GrGpu.h"
 #include "GrAuditTrail.h"
 #include "effects/GrDashingEffect.h"
 
 bool GrDashLinePathRenderer::onCanDrawPath(const CanDrawPathArgs& args) const {
     SkPoint pts[2];
     if (args.fStyle->isDashed() && args.fPath->isLine(pts)) {
         return GrDashingEffect::CanDrawDashLine(pts, *args.fStyle, *args.fViewMatrix);
     }
     return false;
 }
 
 bool GrDashLinePathRenderer::onDrawPath(const DrawPathArgs& args) {
     GR_AUDIT_TRAIL_AUTO_FRAME(args.fDrawContext->auditTrail(),
                               "GrDashLinePathRenderer::onDrawPath");
-    bool msaaIsEnabled = args.fDrawContext->isUnifiedMultisampled();
+    // We always take the msaa codepath, regardless of paint aa, if the platform won't be able to
+    // disable multisampling. Dashes use a mix of msaa and coverage aa, so if we took the bw path in
+    // this case we would wind up with external edges antialiased and internal edges unantialiased.
+    bool useHWAA = args.fDrawContext->isUnifiedMultisampled() &&
+                   (!args.fDrawContext->caps()->multisampleDisableSupport() ||
+                    args.fPaint->isAntiAlias());
+
     GrDashingEffect::AAMode aaMode;
-    if (msaaIsEnabled) {
-        // We ignore args.fAntiAlias here and force anti aliasing when using MSAA. Otherwise,
-        // we can wind up with external edges antialiased and internal edges unantialiased.
+    if (useHWAA) {
         aaMode = GrDashingEffect::AAMode::kCoverageWithMSAA;
     } else if (args.fAntiAlias) {
         aaMode = GrDashingEffect::AAMode::kCoverage;
     } else {
         aaMode = GrDashingEffect::AAMode::kNone;
     }
     SkPoint pts[2];
     SkAssertResult(args.fPath->isLine(pts));
     SkAutoTUnref<GrDrawBatch> batch(GrDashingEffect::CreateDashLineBatch(args.fColor,
                                                                          *args.fViewMatrix,
                                                                          pts,
                                                                          aaMode,
                                                                          *args.fStyle));
     if (!batch) {
         return false;
     }
 
-    GrPipelineBuilder pipelineBuilder(*args.fPaint, msaaIsEnabled);
+    GrPipelineBuilder pipelineBuilder(*args.fPaint, args.fDrawContext->isUnifiedMultisampled());
+    pipelineBuilder.setState(GrPipelineBuilder::kHWAntialias_Flag, useHWAA);
     pipelineBuilder.setUserStencil(args.fUserStencilSettings);
 
     args.fDrawContext->drawBatch(pipelineBuilder, *args.fClip, batch);
     return true;
 }