Fix overdraw debug on QCOM

Disable the use of the tiling extension when overdraw debug is
turned on.

Change-Id: Ib0a0b7d1998146aa0c7efef2d3822f9997efb123
diff --git a/libs/hwui/Caches.cpp b/libs/hwui/Caches.cpp
index 22f1dec..898962a 100644
--- a/libs/hwui/Caches.cpp
+++ b/libs/hwui/Caches.cpp
@@ -435,15 +435,13 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 void Caches::startTiling(GLuint x, GLuint y, GLuint width, GLuint height, bool opaque) {
-    if (extensions.hasTiledRendering()) {
-        glStartTilingQCOM(x, y, width, height,
-                (opaque ? GL_NONE : GL_COLOR_BUFFER_BIT0_QCOM) |
-                (debugOverdraw ? GL_STENCIL_BUFFER_BIT0_QCOM : 0));
+    if (extensions.hasTiledRendering() && !debugOverdraw) {
+        glStartTilingQCOM(x, y, width, height, (opaque ? GL_NONE : GL_COLOR_BUFFER_BIT0_QCOM));
     }
 }
 
 void Caches::endTiling() {
-    if (extensions.hasTiledRendering()) {
+    if (extensions.hasTiledRendering() && !debugOverdraw) {
         glEndTilingQCOM(GL_COLOR_BUFFER_BIT0_QCOM);
     }
 }