gpu: Add CHROMIUM_image support to in-process command buffer.

This makes it possible to use the in-process command buffer
with CHROMIUM_image extension. GpuMemoryBufferManager and
ImageFactory interfaces need to be provided when creating
an in-process command buffer. Existing implementations
of these interfaces in content/ should work just fine.

cc::TestGpuMemoryBufferManager and cc::TestImageFactory
are used for cc pixel tests. They provide a minimal
implementation of these interfaces using shared memory.

Note: shared memory is used for in-process testing as it
maps better to the GpuMemoryBuffer framework that has
been designed for multi-process usage. Non-shared memory
might be a bit more efficient but it would require more
complexity and not match real usage as well.

BUG=423533

Review URL: https://codereview.chromium.org/665463003

Cr-Commit-Position: refs/heads/master@{#301763}

• android_webview/browser/hardware_renderer.cc[diff]
• cc/BUILD.gn[diff]
• cc/cc_tests.gyp[diff]
• cc/test/DEPS[diff]
• cc/test/test_gpu_memory_buffer_manager.cc[diff]
• cc/test/test_gpu_memory_buffer_manager.h[diff]
• cc/test/test_image_factory.cc[Added - diff]
• cc/test/test_image_factory.h[Added - diff]
• cc/test/test_in_process_context_provider.cc[diff]
• cc/test/test_in_process_context_provider.h[diff]
• content/browser/android/in_process/synchronous_compositor_factory_impl.cc[diff]
• gpu/command_buffer/client/gl_in_process_context.cc[diff]
• gpu/command_buffer/client/gl_in_process_context.h[diff]
• gpu/command_buffer/service/in_process_command_buffer.cc[diff]
• gpu/command_buffer/service/in_process_command_buffer.h[diff]
• webkit/common/gpu/webgraphicscontext3d_in_process_command_buffer_impl.cc[diff]