Revert of Remove gpu support for willUseHWAALines.

src/gpu/GrDrawTarget.cpp

Index: src/gpu/GrDrawTarget.cpp
diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index d44c6991b44eb15e4dee2e712bd2d625558d3de2..72204fa14bfecbd81bff6619f709120e96ac4d3d 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -613,16 +613,24 @@
 
 ////////////////////////////////////////////////////////////////////////////////
 
+bool GrDrawTarget::willUseHWAALines() const {
+    // There is a conflict between using smooth lines and our use of premultiplied alpha. Smooth
+    // lines tweak the incoming alpha value but not in a premul-alpha way. So we only use them when
+    // our alpha is 0xff and tweaking the color for partial coverage is OK
+    if (!this->caps()->hwAALineSupport() ||
+        !this->getDrawState().isHWAntialiasState()) {
+        return false;
+    }
+    GrDrawState::BlendOptFlags opts = this->getDrawState().getBlendOpts();
+    return (GrDrawState::kDisableBlend_BlendOptFlag & opts) &&
+           (GrDrawState::kCoverageAsAlpha_BlendOptFlag & opts);
+}
+
 bool GrDrawTarget::canApplyCoverage() const {
     // we can correctly apply coverage if a) we have dual source blending
-    // or b) one of our blend optimizations applies 
-    // or c) the src/dst coefficients are 1, 0 respectively.
-    GrBlendCoeff srcCoeff; 
-    GrBlendCoeff dstCoeff; 
+    // or b) one of our blend optimizations applies.
     return this->caps()->dualSourceBlendingSupport() ||
-           GrDrawState::kNone_BlendOpt != this->getDrawState().getBlendOpts(true, &srcCoeff,
-                                                                            &dstCoeff) ||
-           (kOne_GrBlendCoeff == srcCoeff && kZero_GrBlendCoeff == dstCoeff);
+           GrDrawState::kNone_BlendOpt != this->getDrawState().getBlendOpts(true);
 }
 
 ////////////////////////////////////////////////////////////////////////////////