Use glInvalidateFramebuffer() when it is supported.

src/gpu/gl/GrGpuGL.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGpuGL.h"
 #include "GrGLStencilBuffer.h"
@@ skipping 1278 matching lines @@
     g = GrColorUnpackG(color) * scaleRGB;
     b = GrColorUnpackB(color) * scaleRGB;
 
     GL_CALL(ColorMask(GR_GL_TRUE, GR_GL_TRUE, GR_GL_TRUE, GR_GL_TRUE));
     fHWWriteToColor = kYes_TriState;
     GL_CALL(ClearColor(r, g, b, a));
     GL_CALL(Clear(GR_GL_COLOR_BUFFER_BIT));
 }
 
 void GrGpuGL::discard(GrRenderTarget* renderTarget) {
+    if (!this->caps()->discardRenderTargetSupport()) {
+        return;
+    }
     if (NULL == renderTarget) {
         renderTarget = this->drawState()->getRenderTarget();
         if (NULL == renderTarget) {
             return;
         }
     }
 
     GrGLRenderTarget* glRT = static_cast<GrGLRenderTarget*>(renderTarget);
     if (renderTarget != fHWBoundRenderTarget) {
         fHWBoundRenderTarget = NULL;
         GL_CALL(BindFramebuffer(GR_GL_FRAMEBUFFER, glRT->renderFBOID()));
     }
-    GrGLenum attachments[] = { GR_GL_COLOR };
-    GL_CALL(DiscardFramebuffer(GR_GL_FRAMEBUFFER, SK_ARRAY_COUNT(attachments), attachments));
+    switch (this->glCaps().invalidateFBType()) {
+        case GrGLCaps::kNone_FBFetchType:
+            GrCrash("Should never get here.");
+            break;
+        case GrGLCaps::kInvalidate_InvalidateFBType:
+            if (0 == glRT->renderFBOID()) {
+                //  When rendering to the default framebuffer the legal values for attachments
+                //  are GL_COLOR, GL_DEPTH, GL_STENCIL, ... rather than the various FBO attachment
+                //  types.
+                static const GrGLenum attachments[] = { GR_GL_COLOR };
+                GL_CALL(InvalidateFramebuffer(GR_GL_FRAMEBUFFER, SK_ARRAY_COUNT(attachments),
+                        attachments));
+            } else {
+                static const GrGLenum attachments[] = { GR_GL_COLOR_ATTACHMENT0 };
+                GL_CALL(InvalidateFramebuffer(GR_GL_FRAMEBUFFER, SK_ARRAY_COUNT(attachments),
+                        attachments));
+            }
+            break;
+        case GrGLCaps::kDiscard_InvalidateFBType: {
+            static const GrGLenum attachments[] = { GR_GL_COLOR };
+            GL_CALL(DiscardFramebuffer(GR_GL_FRAMEBUFFER, SK_ARRAY_COUNT(attachments),
+                    attachments));
+            break;
+        }
+    }
     renderTarget->flagAsResolved();
 }
 
 
 void GrGpuGL::clearStencil() {
     if (NULL == this->getDrawState().getRenderTarget()) {
         return;
     }
 
     this->flushRenderTarget(&SkIRect::EmptyIRect());
@@ skipping 1485 matching lines @@
             this->setVertexArrayID(gpu, 0);
         }
         int attrCount = gpu->glCaps().maxVertexAttributes();
         if (fDefaultVertexArrayAttribState.count() != attrCount) {
             fDefaultVertexArrayAttribState.resize(attrCount);
         }
         attribState = &fDefaultVertexArrayAttribState;
     }
     return attribState;
 }