Bug 919987 - Replace mCurSurface, which was redundant state, by a saner mSurfaceOverride that does nothing when it's EGL_NO_SURFACE - r=jgilbert

gfx/gl/GLContext.h

@@ -2449,7 +2449,18 @@ public:
     virtual EGLContext GetEGLContext() { return nullptr; }
     virtual GLLibraryEGL* GetLibraryEGL() { return nullptr; }
 
-    virtual void MakeCurrent_EGLSurface(void* surf) {
+    /**
+     * Only on EGL.
+     *
+     * If surf is non-null, this sets it to temporarily override this context's
+     * primary surface. This makes this context current against this surface,
+     * and subsequent MakeCurrent calls will continue using this surface as long
+     * as this override is set.
+     *
+     * If surf is null, this removes any previously set override, and makes the
+     * context current again against its primary surface.
+     */
+    virtual void SetEGLSurfaceOverride(void* surf) {
         MOZ_CRASH("Must be called against a GLContextEGL.");
     }
 

gfx/gl/GLContextProviderEGL.cpp

@@ -232,7 +232,7 @@ public:
         : GLContext(caps, shareContext, isOffscreen)
         , mConfig(config)
         , mSurface(surface)
-        , mCurSurface(surface)
+        , mSurfaceOverride(EGL_NO_SURFACE)
         , mContext(context)
         , mThebesSurface(nullptr)
         , mBound(false)
@@ -405,15 +405,7 @@ public:
     }
 #endif
 
-    virtual void MakeCurrent_EGLSurface(void* surf) {
-        EGLSurface eglSurface = (EGLSurface)surf;
-        if (!eglSurface)
-            eglSurface = mSurface;
-
-        if (eglSurface == mCurSurface)
-            return;
-
-        // Else, surface changed...
+    virtual void SetEGLSurfaceOverride(void* surf) MOZ_OVERRIDE {
         if (Screen()) {
             /* Blit `draw` to `read` if we need to, before we potentially juggle
              * `read` around. If we don't, we might attach a different `read`,
@@ -423,7 +415,7 @@ public:
             Screen()->AssureBlitted();
         }
 
-        mCurSurface = eglSurface;
+        mSurfaceOverride = surf ? (EGLSurface) surf : mSurface;
         MakeCurrent(true);
     }
 
@@ -434,10 +426,12 @@ public:
         // where MakeCurrent with an already-current context is
         // still expensive.
         if (aForce || sEGLLibrary.fGetCurrentContext() != mContext) {
+            EGLSurface surface = mSurfaceOverride != EGL_NO_SURFACE
+                                 ? mSurfaceOverride
+                                 : mSurface;
             succeeded = sEGLLibrary.fMakeCurrent(EGL_DISPLAY(),
-                                                 mCurSurface, mCurSurface,
+                                                 surface, surface,
                                                  mContext);
-            
             int eglError = sEGLLibrary.fGetError();
             if (!succeeded) {
                 if (eglError == LOCAL_EGL_CONTEXT_LOST) {
@@ -577,7 +571,7 @@ protected:
 
     EGLConfig  mConfig;
     EGLSurface mSurface;
-    EGLSurface mCurSurface;
+    EGLSurface mSurfaceOverride;
     EGLContext mContext;
     nsRefPtr<gfxASurface> mThebesSurface;
     bool mBound;

gfx/gl/SharedSurfaceANGLE.cpp

@@ -45,7 +45,7 @@ SharedSurface_ANGLEShareHandle::~SharedSurface_ANGLEShareHandle()
 void
 SharedSurface_ANGLEShareHandle::LockProdImpl()
 {
-    mGL->MakeCurrent_EGLSurface(mPBuffer);
+    mGL->SetEGLSurfaceOverride(mPBuffer);
 }
 
 void