Fix Coverity reports.  (Mostly use of uninitialised values.)

CID=537,103419,103631,103632,103633

Review URL: https://codereview.appspot.com/5936047

git-svn-id: http://skia.googlecode.com/svn/trunk@3522 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrAAConvexPathRenderer.cpp b/src/gpu/GrAAConvexPathRenderer.cpp
index 7638067..7f8d027 100644
--- a/src/gpu/GrAAConvexPathRenderer.cpp
+++ b/src/gpu/GrAAConvexPathRenderer.cpp
@@ -53,10 +53,9 @@
 
 void center_of_mass(const SegmentArray& segments, SkPoint* c) {
     GrScalar area = 0;
-    SkPoint center;
-    center.set(0, 0);
+    SkPoint center = {};
     int count = segments.count();
-    SkPoint p0;
+    SkPoint p0 = {};
     if (count > 2) {
         // We translate the polygon so that the first point is at the origin.
         // This avoids some precision issues with small area polygons far away