Implement SkGLContext swapBuffers with fence syncs

src/gpu/gl/mac/SkCreatePlatformGLContext_mac.cpp

Index: src/gpu/gl/mac/SkCreatePlatformGLContext_mac.cpp
diff --git a/src/gpu/gl/mac/SkCreatePlatformGLContext_mac.cpp b/src/gpu/gl/mac/SkCreatePlatformGLContext_mac.cpp
index 436c53f0bb2fea88e9a9ead8bbc97acd7185cd5f..d2d8569938665b8689d112a503707a0e391c8b72 100644
--- a/src/gpu/gl/mac/SkCreatePlatformGLContext_mac.cpp
+++ b/src/gpu/gl/mac/SkCreatePlatformGLContext_mac.cpp
@@ -9,23 +9,28 @@
 #include "AvailabilityMacros.h"
 
 #include <OpenGL/OpenGL.h>
+#include <dlfcn.h>
 
 namespace {
 class MacGLContext : public SkGLContext {
 public:
     MacGLContext();
     ~MacGLContext() override;
-    void makeCurrent() const override;
-    void swapBuffers() const override;
 
 private:
     void destroyGLContext();
 
+    void onPlatformMakeCurrent() const override;
+    void onPlatformSwapBuffers() const override;
+    GrGLFuncPtr onPlatformGetProcAddress(const char*) const override;
+
     CGLContextObj fContext;
+    void* fGLLibrary;
 };
 
 MacGLContext::MacGLContext()
-    : fContext(NULL) {
+    : fContext(NULL)
+    , fGLLibrary(RTLD_DEFAULT) {
     CGLPixelFormatAttribute attributes[] = {
 #if MAC_OS_X_VERSION_10_7
         kCGLPFAOpenGLProfile, (CGLPixelFormatAttribute) kCGLOGLPVersion_3_2_Core,
@@ -53,39 +58,52 @@ MacGLContext::MacGLContext()
 
     CGLSetCurrentContext(fContext);
 
-    fGL.reset(GrGLCreateNativeInterface());
-    if (NULL == fGL.get()) {
+    SkAutoTUnref<const GrGLInterface> gl(GrGLCreateNativeInterface());
+    if (NULL == gl.get()) {
         SkDebugf("Context could not create GL interface.\n");
         this->destroyGLContext();
         return;
     }
-    if (!fGL->validate()) {
+    if (!gl->validate()) {
         SkDebugf("Context could not validate GL interface.\n");
         this->destroyGLContext();
         return;
     }
+
+    fGLLibrary = dlopen(
+        "/System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib",
+        RTLD_LAZY);
+
+    this->init(gl.detach());
 }
 
 MacGLContext::~MacGLContext() {
+    this->teardown();
     this->destroyGLContext();
 }
 
 void MacGLContext::destroyGLContext() {
-    fGL.reset(NULL);
     if (fContext) {
         CGLReleaseContext(fContext);
         fContext = NULL;
     }
+    if (RTLD_DEFAULT != fGLLibrary) {
+        dlclose(fGLLibrary);
+    }
 }
 
-void MacGLContext::makeCurrent() const {
+void MacGLContext::onPlatformMakeCurrent() const {
     CGLSetCurrentContext(fContext);
 }
 
-void MacGLContext::swapBuffers() const {
+void MacGLContext::onPlatformSwapBuffers() const {
     CGLFlushDrawable(fContext);
 }
 
+GrGLFuncPtr MacGLContext::onPlatformGetProcAddress(const char* procName) const {
+    return reinterpret_cast<GrGLFuncPtr>(dlsym(fGLLibrary, procName));
+}
+
 } // anonymous namespace
 
 SkGLContext* SkCreatePlatformGLContext(GrGLStandard forcedGpuAPI) {