Fix off-by-one error in assertion; improve coverage_to_exact_alpha()
implementation.

http://codereview.appspot.com/5504116/



git-svn-id: http://skia.googlecode.com/svn/trunk@2947 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkBlitter.cpp b/src/core/SkBlitter.cpp
index 8bb4b4f..ec16066 100644
--- a/src/core/SkBlitter.cpp
+++ b/src/core/SkBlitter.cpp
@@ -487,7 +487,7 @@
         const SkIRect& r = iter.rect();
         SkASSERT(bounds.contains(r));
         SkASSERT(r.fLeft >= x);
-        SkASSERT(r.fRight < x + width + 2);
+        SkASSERT(r.fRight <= x + width + 2);
 
         SkAlpha effectiveLeftAlpha = (r.fLeft == x) ? leftAlpha : 255;
         SkAlpha effectiveRightAlpha = (r.fRight == x + width + 2) ?