Basic error checking for debugger GL widget.

debugger/QT/SkGLWidget.cpp

Index: debugger/QT/SkGLWidget.cpp
===================================================================
--- debugger/QT/SkGLWidget.cpp	(revision 9826)
+++ debugger/QT/SkGLWidget.cpp	(working copy)
@@ -29,6 +29,9 @@
 
 void SkGLWidget::initializeGL() {
     fCurIntf = GrGLCreateNativeInterface();
+    if (!fCurIntf) {
+        return;
+    }
     fCurContext = GrContext::Create(kOpenGL_GrBackend, (GrBackendContext) fCurIntf);
     GrBackendRenderTargetDesc desc = this->getDesc(this->width(), this->height());
     desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
@@ -43,19 +46,21 @@
 }
 
 void SkGLWidget::resizeGL(int w, int h) {
-    GrBackendRenderTargetDesc desc = this->getDesc(w, h);
-    desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
-    GrRenderTarget* curRenderTarget = fCurContext->wrapBackendRenderTarget(desc);
-    SkSafeUnref(fGpuDevice);
-    SkSafeUnref(fCanvas);
-    fGpuDevice = new SkGpuDevice(fCurContext, curRenderTarget);
-    fCanvas = new SkCanvas(fGpuDevice);
+    if (fCurContext) {
+        GrBackendRenderTargetDesc desc = this->getDesc(w, h);
+        desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
+        GrRenderTarget* curRenderTarget = fCurContext->wrapBackendRenderTarget(desc);
+        SkSafeUnref(fGpuDevice);
+        SkSafeUnref(fCanvas);
+        fGpuDevice = new SkGpuDevice(fCurContext, curRenderTarget);
+        fCanvas = new SkCanvas(fGpuDevice);
+    }
     fDebugger->resize(w, h);
     draw();
 }
 
 void SkGLWidget::paintGL() {
-    if (!this->isHidden()) {
+    if (!this->isHidden() && fCanvas) {
         fDebugger->draw(fCanvas);
         // TODO(chudy): Implement an optional flush button in Gui.
         fCanvas->flush();