From a595a7e43ddf1b9f9e1f79debd47567797bb68db Mon Sep 17 00:00:00 2001
From: "Carsten \"Tomcat\" Book" <cbook@mozilla.com>
Date: Mon, 16 Mar 2015 11:28:46 +0100
Subject: [PATCH] Backed out changeset c7d73cfc59cb (bug 927995)

---
 gfx/gl/GLScreenBuffer.cpp | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/gfx/gl/GLScreenBuffer.cpp b/gfx/gl/GLScreenBuffer.cpp
index 51145adc51d..569d3dce5c4 100755
--- a/gfx/gl/GLScreenBuffer.cpp
+++ b/gfx/gl/GLScreenBuffer.cpp
@@ -403,18 +403,7 @@ GLScreenBuffer::Attach(SharedSurface* surf, const gfx::IntSize& size)
     } else {
         // Else something changed, so resize:
         UniquePtr<DrawBuffer> draw;
-        bool drawOk = true;
-
-        /* Don't change out the draw buffer unless we resize. In the
-         * preserveDrawingBuffer:true case, prior contents of the buffer must
-         * be retained. If we're using a draw buffer, it's an MSAA buffer, so
-         * even if we copy the previous frame into the (single-sampled) read
-         * buffer, if we need to re-resolve from draw to read (as triggered by
-         * drawing), we'll need the old MSAA content to still be in the draw
-         * buffer.
-         */
-        if (!mDraw || size != Size())
-            drawOk = CreateDraw(size, &draw);  // Can be null.
+        bool drawOk = CreateDraw(size, &draw);  // Can be null.
 
         UniquePtr<ReadBuffer> read = CreateRead(surf);
         bool readOk = !!read;
@@ -425,9 +414,7 @@ GLScreenBuffer::Attach(SharedSurface* surf, const gfx::IntSize& size)
             return false;
         }
 
-        if (draw)
-            mDraw = Move(draw);
-
+        mDraw = Move(draw);
         mRead = Move(read);
     }
 
@@ -440,8 +427,6 @@ GLScreenBuffer::Attach(SharedSurface* surf, const gfx::IntSize& size)
         mRead->SetReadBuffer(mUserReadBufferMode);
     }
 
-    RequireBlit();
-
     return true;
 }
 
@@ -465,8 +450,7 @@ GLScreenBuffer::Swap(const gfx::IntSize& size)
 
     if (ShouldPreserveBuffer() &&
         mFront &&
-        mBack &&
-        !mDraw)
+        mBack)
     {
         auto src  = mFront->Surf();
         auto dest = mBack->Surf();