Changed '0.5f' to '0.5' in conical gradient shader to fix problem with shader compile on Mac.

git-svn-id: http://skia.googlecode.com/svn/trunk@4444 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/effects/GrGradientEffects.cpp b/src/gpu/effects/GrGradientEffects.cpp
index 005002f..f9fd4d2 100644
--- a/src/gpu/effects/GrGradientEffects.cpp
+++ b/src/gpu/effects/GrGradientEffects.cpp
@@ -497,7 +497,7 @@
 
         // intermediate value we'll use to compute the roots
         // q = -0.5 * (b +/- sqrt(d))
-        code->appendf("\tfloat %s = -0.5f * (%s + (%s < 0.0 ? -1.0 : 1.0)"
+        code->appendf("\tfloat %s = -0.5 * (%s + (%s < 0.0 ? -1.0 : 1.0)"
                       " * sqrt(%s));\n", qName.c_str(), bVar.c_str(), 
                       bVar.c_str(), dName.c_str());