Quick reject empty paths

bug:7260035

Adding a circle of radius 0 to a path is a no-op in skia, so detect
this case both in the PathRenderer, and in quickReject().

Change-Id: I7a172db49a5d5351b4734b39d4e4ca6379658096
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index c015077..c2e6ee3 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -1265,7 +1265,7 @@
 }
 
 bool OpenGLRenderer::quickReject(float left, float top, float right, float bottom) {
-    if (mSnapshot->isIgnored()) {
+    if (mSnapshot->isIgnored() || bottom <= top || right <= left) {
         return true;
     }
 
@@ -1951,6 +1951,11 @@
     // TODO: try clipping large paths to viewport
     PathRenderer::convexPathVertices(path, paint, mSnapshot->transform, vertexBuffer);
 
+    if (!vertexBuffer.getSize()) {
+        // no vertices to draw
+        return;
+    }
+
     setupDraw();
     setupDrawNoTexture();
     if (isAA) setupDrawAA();