When we create the GL context and FBO on mac for the GM test also setup the viewport and clear the stencil.
In GrGpuGL::readPixels make sure current rendertarget has been made current in GL before calling glReadPixels



git-svn-id: http://skia.googlecode.com/svn/trunk@761 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/GrGpuGL.cpp b/gpu/src/GrGpuGL.cpp
index 3d86d1b..d366953 100644
--- a/gpu/src/GrGpuGL.cpp
+++ b/gpu/src/GrGpuGL.cpp
@@ -271,7 +271,7 @@
     // these a preprocess that generate some compile time constants.
 
     // sanity check to make sure we can at least create an FBO from a POT texture
-    
+
     bool simpleFBOSuccess = fbo_test(fExts, 128, 128);
     if (gPrintStartupSpew) {
         if (!simpleFBOSuccess) {
@@ -293,7 +293,7 @@
     if (fNPOTTextureSupport) {
         fNPOTRenderTargetSupport = fbo_test(fExts, 200, 200);
     }
-    
+
     if (gPrintStartupSpew) {
         if (fNPOTTextureSupport) {
             GrPrintf("NPOT textures supported\n");
@@ -1053,7 +1053,11 @@
         return false;
     }
 
-    GrAssert(NULL != fCurrDrawState.fRenderTarget);
+    if (NULL == fCurrDrawState.fRenderTarget) {
+        return false;
+    }
+    flushRenderTarget();
+
     const GrIRect& vp = ((GrGLRenderTarget*)fCurrDrawState.fRenderTarget)->viewport();
 
     // Brian says that viewport rects are already upside down (grrrrr)