Make SkOSWindow return the sample count and stencil bit count for its GL context.

experimental/iOSSampleApp/SkSampleUIView.mm

Index: experimental/iOSSampleApp/SkSampleUIView.mm
===================================================================
--- experimental/iOSSampleApp/SkSampleUIView.mm	(revision 7991)
+++ experimental/iOSSampleApp/SkSampleUIView.mm	(working copy)
@@ -61,8 +61,8 @@
                 SkASSERT(false);
                 break;
         }
-        
-        bool result = win->attach(fBackend, msaaSampleCount);
+        SkOSWindow::AttachmentInfo info;
+        bool result = win->attach(fBackend, msaaSampleCount, &info);
         if (!result) {
             SkDebugf("Failed to initialize GL");
             return;
@@ -165,7 +165,9 @@
     virtual void windowSizeChanged(SampleWindow* win) SK_OVERRIDE {
 #if SK_SUPPORT_GPU
         if (NULL != fCurContext) {
-            win->attach(fBackend, fMSAASampleCount);
+            SkOSWindow::AttachmentInfo info;
+
+            win->attach(fBackend, fMSAASampleCount, &info);
             
             glBindFramebuffer(GL_FRAMEBUFFER, fLayerFBO);
             GrBackendRenderTargetDesc desc;
@@ -173,9 +175,9 @@
             desc.fHeight = SkScalarRound(win->height());
             desc.fConfig = kSkia8888_GrPixelConfig;
             desc.fRenderTargetHandle = fLayerFBO;
-            glGetIntegerv(GL_SAMPLES, &desc.fSampleCnt);
-            glGetIntegerv(GL_STENCIL_BITS, &desc.fStencilBits);
-            
+            desc.fSampleCnt = info.fSampleCount;
+            desc.fStencilBits = info.fStencilBits;
+
             SkSafeUnref(fCurRenderTarget);
             fCurRenderTarget = fCurContext->wrapBackendRenderTarget(desc);
         }
@@ -480,4 +482,14 @@
     }
 }
 
+- (void)getAttachmentInfo:(SkOSWindow::AttachmentInfo*)info {
+    glBindRenderbuffer(GL_RENDERBUFFER, fGL.fRenderbuffer);
+    glGetRenderbufferParameteriv(GL_RENDERBUFFER,
+                                 GL_RENDERBUFFER_STENCIL_SIZE,
+                                 &info->fStencilBits);
+    glGetRenderbufferParameteriv(GL_RENDERBUFFER,
+                                 GL_RENDERBUFFER_SAMPLES_APPLE,
+                                 &info->fSampleCount);
+}
+
 @end