Pull xfer mode test out of generic draw-as-hairline test. Use coverage rather than alpha to draw hairlines < 1pix wide in GPU.

Review URL: http://codereview.appspot.com/5528112/




git-svn-id: http://skia.googlecode.com/svn/trunk@3070 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrPaint.h b/include/gpu/GrPaint.h
index f1d74b2..9f220e0 100644
--- a/include/gpu/GrPaint.h
+++ b/include/gpu/GrPaint.h
@@ -36,6 +36,7 @@
     bool                        fColorMatrixEnabled;
 
     GrColor                     fColor;
+    uint8_t                     fCoverage;
 
     GrColor                     fColorFilterColor;
     SkXfermode::Mode            fColorFilterXfermode;
@@ -126,6 +127,7 @@
         fDither = paint.fDither;
 
         fColor = paint.fColor;
+        fCoverage = paint.fCoverage;
 
         fColorFilterColor = paint.fColorFilterColor;
         fColorFilterXfermode = paint.fColorFilterXfermode;
@@ -161,6 +163,7 @@
         this->resetBlend();
         this->resetOptions();
         this->resetColor();
+        this->resetCoverage();
         this->resetTextures();
         this->resetColorFilter();
         this->resetMasks();
@@ -242,6 +245,10 @@
         fColor = GrColorPackRGBA(0xff, 0xff, 0xff, 0xff);
     }
 
+    void resetCoverage() {
+        fCoverage = 0xff;
+    }
+
     void resetTextures() {
         for (int i = 0; i < kMaxTextures; ++i) {
             this->setTexture(i, NULL);