It's also fixed when unconditionally calling gl_->BindFramebuffer(GL_FRAMEBUFFER, fbo_); at the end of DrawingBuffer::ResolveIfNeeded(). I tried that after reading the behavioral change zmo@ expressed concern about in https://codereview.chromium.org/2597933002.

Capn, thank you for giving me so much useful info.
I had debugged this issue, GL_INVALID_OPERATION happens when readPixels, because framebuffer is binding to multisample_fbo_, It should bind to fbo_.

As my comments in https://codereview.chromium.org/2597933002, I think it is the callers' responsibility to manage the binding status, so I give another patch to handle this issue, https://codereview.chromium.org/2905633002/
@kbr & @zmo, please help to review this patch, thank you.

Blocking the bug in which the original change was made. Seems like there were a couple of issues with that patch.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f4f805f9fb47f434766195909c50a46b484ffdbb

commit f4f805f9fb47f434766195909c50a46b484ffdbb
Author: xinghua.cao <xinghua.cao@intel.com>
Date: Fri Jun 02 21:59:59 2017

Bind framebuffer to fbo_ object before readPixels, rather than multisample_fbo_

readPixels cannot get content from multisample_fbo_ directly, only from fbo_ whose
content is resolved from multisample_fbo_.

BUG= 725579 
TESTCASE=DrawingBufferSoftwareRenderingTest.framebufferBinding

Review-Url: https://codereview.chromium.org/2905633002
Cr-Commit-Position: refs/heads/master@{#476807}

[modify] https://crrev.com/f4f805f9fb47f434766195909c50a46b484ffdbb/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
[modify] https://crrev.com/f4f805f9fb47f434766195909c50a46b484ffdbb/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferSoftwareRenderingTest.cpp
[modify] https://crrev.com/f4f805f9fb47f434766195909c50a46b484ffdbb/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTest.cpp
[modify] https://crrev.com/f4f805f9fb47f434766195909c50a46b484ffdbb/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h

 Issue 728092  has been merged into this issue.

xinghua, is this fixed now?

Hi, vmiura, the patch had been merged. It should be fixed now.

Thanks!

Fix landed in M61 not M60: https://storage.googleapis.com/chromium-find-releases-static/f4f.html#f4f805f9fb47f434766195909c50a46b484ffdbb

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/33e2e848ee23a2d32462733a891f7274ac2290c0

commit 33e2e848ee23a2d32462733a891f7274ac2290c0
Author: Michael Moss <mmoss@google.com>
Date: Thu Aug 10 23:17:52 2017

Bind framebuffer to fbo_ object before readPixels, rather than multisample_fbo_

readPixels cannot get content from multisample_fbo_ directly, only from fbo_ whose
content is resolved from multisample_fbo_.

BUG= 725579 
TESTCASE=DrawingBufferSoftwareRenderingTest.framebufferBinding
TBR=xinghua.cao@intel.com

(cherry picked from commit f4f805f9fb47f434766195909c50a46b484ffdbb)

Review-Url: https://codereview.chromium.org/2905633002
Cr-Original-Commit-Position: refs/heads/master@{#476807}
Change-Id: I54007f9cb79aefdc842b6caa4e8389f30754d9d7
Reviewed-on: https://chromium-review.googlesource.com/611322
Reviewed-by: Michael Moss <mmoss@chromium.org>
Cr-Commit-Position: refs/branch-heads/3112@{#722}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
[modify] https://crrev.com/33e2e848ee23a2d32462733a891f7274ac2290c0/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
[modify] https://crrev.com/33e2e848ee23a2d32462733a891f7274ac2290c0/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferSoftwareRenderingTest.cpp
[modify] https://crrev.com/33e2e848ee23a2d32462733a891f7274ac2290c0/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTest.cpp
[modify] https://crrev.com/33e2e848ee23a2d32462733a891f7274ac2290c0/third_party/WebKit/Source/platform/graphics/gpu/DrawingBufferTestHelpers.h

 Issue 760001  has been merged into this issue.