Refactor SkGLContext to be actually extendable

src/gpu/gl/iOS/SkCreatePlatformGLContext_iOS.mm

Index: src/gpu/gl/iOS/SkCreatePlatformGLContext_iOS.mm
diff --git a/src/gpu/gl/iOS/SkCreatePlatformGLContext_iOS.mm b/src/gpu/gl/iOS/SkCreatePlatformGLContext_iOS.mm
index 9989957ac9ea684fdebb2539dc2c9f99df6c9edf..423ef8cbddfc0efaa9532a72544c9d8d9f1182f3 100644
--- a/src/gpu/gl/iOS/SkCreatePlatformGLContext_iOS.mm
+++ b/src/gpu/gl/iOS/SkCreatePlatformGLContext_iOS.mm
@@ -16,21 +16,33 @@ namespace {
 class IOSGLContext : public SkGLContext {
 public:
     IOSGLContext();
-
-    virtual ~IOSGLContext();
-
+    virtual ~IOSGLContext() SK_OVERRIDE;
     virtual void makeCurrent() const SK_OVERRIDE;
     virtual void swapBuffers() const SK_OVERRIDE;
-protected:
-    virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) SK_OVERRIDE;
-    virtual void destroyGLContext() SK_OVERRIDE;
 
 private:
+    void destroyGLContext();
+
     void* fEAGLContext;
 };
 
 IOSGLContext::IOSGLContext()
     : fEAGLContext(NULL) {
+
+    fEAGLContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
+    [EAGLContext setCurrentContext:EAGLCTX];
+
+    fGL.reset(GrGLCreateNativeInterface());
+    if (NULL == fGL.get()) {
+        SkDebugf("Failed to create gl interface");
+        this->destroyGLContext();
+        return;
+    }
+    if (!fGL->validate()) {
+        SkDebugf("Failed to validate gl interface");
+        this->destroyGLContext();
+        return;
+    }
 }
 
 IOSGLContext::~IOSGLContext() {
@@ -38,6 +50,7 @@ IOSGLContext::~IOSGLContext() {
 }
 
 void IOSGLContext::destroyGLContext() {
+    fGL.reset(NULL);
     if (fEAGLContext) {
         if ([EAGLContext currentContext] == EAGLCTX) {
             [EAGLContext setCurrentContext:nil];
@@ -47,22 +60,6 @@ void IOSGLContext::destroyGLContext() {
     }
 }
 
-const GrGLInterface* IOSGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
-    if (kGL_GrGLStandard == forcedGpuAPI) {
-        return NULL;
-    }
-
-    fEAGLContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
-    [EAGLContext setCurrentContext:EAGLCTX];
-    
-    const GrGLInterface* interface = GrGLCreateNativeInterface();
-    if (!interface) {
-        SkDebugf("Failed to create gl interface");
-        this->destroyGLContext();
-        return NULL;
-    }
-    return interface;
-}
 
 void IOSGLContext::makeCurrent() const {
     if (![EAGLContext setCurrentContext:EAGLCTX]) {
@@ -74,8 +71,15 @@ void IOSGLContext::swapBuffers() const { }
 
 } // anonymous namespace
 
-
-SkGLContext* SkCreatePlatformGLContext() {
-    return SkNEW(IOSGLContext);
+SkGLContext* SkCreatePlatformGLContext(GrGLStandard forcedGpuAPI) {
+    if (kGL_GrGLStandard == forcedGpuAPI) {
+        return NULL;
+    }
+    IOSGLContext* ctx = SkNEW(IOSGLContext);
+    if (!ctx->isValid()) {
+        SkDELETE(ctx);
+        return NULL;
+    }
+    return ctx;
 }