Chrome Version: 65.0.3325.162
OS: macOS 10.12.5 and 10.13.3

What steps will reproduce the problem?
(1) Launch content_shell on a MacBook Pro with dual GPUs (for example, "Intel Iris Pro 1536 MB" / "AMD Radeon R9 M370X 2 GB" GPUs).

What is the expected result?
Discrete GPU should not be activated on startup (Activity Monitor should not show "Requires High Perf GPU").

What happens instead?
Discrete GPU is activated. In Chrome something is triggering an immediate switch back to the integrated GPU. In content_shell the discrete GPU remains active. Keeping the discrete GPU active significantly reduces battery life.

Please use labels and text to provide additional information.

Related discussion on graphics-dev: https://groups.google.com/a/chromium.org/d/msg/graphics-dev/lYmc1Fcs5xQ/BgrpgF7sBAAJ

InitializeOnOffForSandbox [1] is calling CGLChoosePixelFormat with an empty CGLPixelFormatAttribute array due to  GLContext::SwitchableGPUsSupported returning false (SetSwitchableGPUsSupported [2] is called later in the startup process). This activates the discrete GPU.

Chrome printf logging:

CGDisplayRegisterReconfigurationCallback
InitializeOneOffForSandbox
InitializeOneOffForSandbox CGLChoosePixelFormat  << empty CGLPixelFormatAttribute array
DisplayReconfigCallback flags=1d
DisplayReconfigCallback flags=1d
DisplayReconfigCallback flags=8476d
DisplayReconfigCallback gpu_changed=1  << switch to discrete GPU
GpuDataManagerImplPrivate::HandleGpuSwitch
GpuSwitchingManager::NotifyGpuSwitched
DisplayReconfigCallback flags=8736d
DisplayReconfigCallback gpu_changed=0
InitializeOneOffForSandbox CGLChoosePixelFormat success
DisplayReconfigCallback flags=1d
DisplayReconfigCallback flags=1d
DisplayReconfigCallback flags=8476d
DisplayReconfigCallback gpu_changed=1  << switch to integrated GPU (not sure what causes this)
GpuDataManagerImplPrivate::HandleGpuSwitch
GpuSwitchingManager::NotifyGpuSwitched
DisplayReconfigCallback flags=8736d
DisplayReconfigCallback gpu_changed=0
InitializeSwitchableGPUs  << call SetSwitchableGPUsSupported

content_shell printf logging:

CGDisplayRegisterReconfigurationCallback
InitializeOneOffForSandbox
InitializeOneOffForSandbox CGLChoosePixelFormat  << empty CGLPixelFormatAttribute array
DisplayReconfigCallback flags=1d
DisplayReconfigCallback flags=1d
DisplayReconfigCallback flags=8476d
DisplayReconfigCallback gpu_changed=1  << switch to discrete GPU
GpuDataManagerImplPrivate::HandleGpuSwitch
GpuSwitchingManager::NotifyGpuSwitched
DisplayReconfigCallback flags=8736d
DisplayReconfigCallback gpu_changed=0
InitializeOneOffForSandbox CGLChoosePixelFormat success
InitializeSwitchableGPUs  << call SetSwitchableGPUsSupported

From https://developer.apple.com/library/content/documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_pixelformats/opengl_pixelformats.html :

"Adding the attribute NSOpenGLPFAAllowOfflineRenderers allows OpenGL to include offline renderers in the list of virtual screens returned in the pixel format object. Apple recommends you include this attribute, because it allows your application to work better in environments where renderers come and go, such as when a new display is plugged into a Mac."

So it sounds like always setting kCGLPFAAllowOfflineRenderers might be safe. I'm running a trial of this currently in a Chromium-based application [4]

There also appears to be an unrelated bug in IOSurfaceContext::Get [3] where it adds the "end of array" 0 value twice.

[1] https://cs.chromium.org/chromium/src/ui/gl/init/gl_initializer_mac.cc?type=cs&q=InitializeOneOffForSandbox&l=40

[2] https://cs.chromium.org/chromium/src/gpu/config/gpu_switching.cc?type=cs&q=SetSwitchableGPUsSupported&l=82

[3] https://cs.chromium.org/chromium/src/ui/accelerated_widget_mac/io_surface_context.mm?type=cs&q=CGLChoosePixelFormat&l=51 

[4] https://bitbucket.org/chromiumembedded/cef/issues/2398