Revert "[Fuchsia] Disable fallback to SW compositing."

This reverts commit 34173c24.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> [Fuchsia] Disable fallback to SW compositing.
> 
> Previously WebEngine was falling back to SW compositing after 3
> GPU process crashes. This is not desirable when Vulkan is enabled
> because it may mask other issues. Also not all features work correctly
> with SW compositing (e.g. it's not compatible with HW video decoder).
> 
> Also added --disable-software-rasterizer to disable SwiftShader as
> we should never need to use it on Fuchsia.
> 
> Bug: 1021844
> Change-Id: I3257d9f0372789849a2922b514e6b23e08a380e0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1854893
> Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
> Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
> Reviewed-by: Wez <wez@chromium.org>
> Reviewed-by: Jonathan Backer <backer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#713063}

TBR=backer@chromium.org,wez@chromium.org,sergeyu@chromium.org

Change-Id: Ie22e4f3afcbf204dbdaf03f34ebb33254be51c0b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1021844
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900663Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713080}

content/browser/gpu/gpu_data_manager_impl_private.cc

@@ -966,12 +966,10 @@ gpu::GpuMode GpuDataManagerImplPrivate::GetGpuMode() const {
 }
 
 void GpuDataManagerImplPrivate::FallBackToNextGpuMode() {
-#if defined(OS_ANDROID) || defined(OS_CHROMEOS) || defined(OS_FUCHSIA)
+#if defined(OS_ANDROID) || defined(OS_CHROMEOS)
   // Android and Chrome OS can't switch to software compositing. If the GPU
   // process initialization fails or GPU process is too unstable then crash the
   // browser process to reset everything.
-  // On Fuchsia Vulkan must be used when it's enabled by the WebEngine embedder.
-  // Falling back to SW compositing in that case is not supported.
 #if defined(OS_ANDROID)
   FatalGpuProcessLaunchFailureOnBackground();
 #endif

fuchsia/engine/context_provider_impl.cc

@@ -247,20 +247,14 @@ void ContextProviderImpl::Create(
   }
 
   if (enable_vulkan) {
-    DLOG(ERROR) << "Enabling Vulkan GPU acceleration.";
     launch_command.AppendSwitch(switches::kUseVulkan);
     launch_command.AppendSwitchASCII(switches::kEnableFeatures,
                                      features::kUseSkiaRenderer.name);
     launch_command.AppendSwitch(switches::kEnableOopRasterization);
-    launch_command.AppendSwitch(switches::kDisableSoftwareRasterizer);
     launch_command.AppendSwitchASCII(switches::kUseGL,
                                      gl::kGLImplementationStubName);
     launch_command.AppendSwitchASCII(switches::kGrContextType,
                                      switches::kGrContextTypeVulkan);
-  } else {
-    DLOG(ERROR) << "Disabling GPU acceleration.";
-    launch_command.AppendSwitch(switches::kDisableGpu);
-    launch_command.AppendSwitch(switches::kDisableSoftwareRasterizer);
   }
 
   if (enable_widevine) {

fuchsia/runners/BUILD.gn

@@ -28,20 +28,6 @@ buildflag_header("buildflags") {
   visibility = [ ":*" ]
 }
 
-# TODO(https://crbug.com/1021844): Remove this hack once we have Vulkan
-# emulation available via AEMU.
-source_set("detect_vulkan_hack") {
-  sources = [
-    "common/detect_vulkan_hack.cc",
-    "common/detect_vulkan_hack.h",
-  ]
-  deps = [
-    "//gpu/vulkan",
-    "//third_party/fuchsia-sdk/sdk:web",
-  ]
-  visibility = [ ":*" ]
-}
-
 # Files common to both cast_runner and web_runner targets.
 source_set("common") {
   sources = [
@@ -106,7 +92,6 @@ executable("cast_runner_exe") {
     ":buildflags",
     ":cast_runner_core",
     ":common",
-    ":detect_vulkan_hack",
     "//base",
     "//fuchsia/base",
   ]
@@ -221,7 +206,6 @@ executable("web_runner_exe") {
   ]
   deps = [
     ":common",
-    ":detect_vulkan_hack",
     "//base",
     "//fuchsia/base",
   ]

fuchsia/runners/cast/main.cc

@@ -13,7 +13,6 @@
 #include "fuchsia/base/init_logging.h"
 #include "fuchsia/runners/buildflags.h"
 #include "fuchsia/runners/cast/cast_runner.h"
-#include "fuchsia/runners/common/detect_vulkan_hack.h"
 
 int main(int argc, char** argv) {
   base::SingleThreadTaskExecutor io_task_executor(base::MessagePumpType::IO);
@@ -32,9 +31,6 @@ int main(int argc, char** argv) {
       fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER |
       fuchsia::web::ContextFeatureFlags::WIDEVINE_CDM;
 
-  // Vulkan is not currently available in our integration test environment.
-  DisableVulkanIfUnavailable(&features);
-
   if (!BUILDFLAG(ENABLE_SOFTWARE_VIDEO_DECODERS))
     features |= fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER_ONLY;
 

fuchsia/runners/common/DEPS

-include_rules = [
-  "+gpu/vulkan",
-]

fuchsia/runners/common/detect_vulkan_hack.cc

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "fuchsia/runners/common/detect_vulkan_hack.h"
-#include "gpu/vulkan/vulkan_function_pointers.h"
-
-// Removes the VULKAN feature flag if Vulkan is not available on the host.
-void DisableVulkanIfUnavailable(fuchsia::web::ContextFeatureFlags* features) {
-  gpu::VulkanFunctionPointers* vulkan_ptrs = gpu::GetVulkanFunctionPointers();
-  if (!vulkan_ptrs->BindUnassociatedFunctionPointers())
-    *features &= ~fuchsia::web::ContextFeatureFlags::VULKAN;
-}

fuchsia/runners/common/detect_vulkan_hack.h

-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef FUCHSIA_RUNNERS_COMMON_DETECT_VULKAN_HACK_H_
-#define FUCHSIA_RUNNERS_COMMON_DETECT_VULKAN_HACK_H_
-
-#include <fuchsia/web/cpp/fidl.h>
-
-// Removes the VULKAN feature flag if Vulkan is not available on the host.
-// TODO(https://crbug.com/1021844): Remove this workaround once our test
-// environment provides Vulkan.
-void DisableVulkanIfUnavailable(fuchsia::web::ContextFeatureFlags* features);
-
-#endif  // FUCHSIA_RUNNERS_COMMON_DETECT_VULKAN_HACK_H_

fuchsia/runners/web/main.cc

@@ -10,7 +10,6 @@
 #include "base/run_loop.h"
 #include "base/task/single_thread_task_executor.h"
 #include "fuchsia/base/init_logging.h"
-#include "fuchsia/runners/common/detect_vulkan_hack.h"
 #include "fuchsia/runners/common/web_content_runner.h"
 
 int main(int argc, char** argv) {
@@ -23,19 +22,17 @@ int main(int argc, char** argv) {
     return 1;
   }
 
-  fuchsia::web::ContextFeatureFlags features =
+  constexpr fuchsia::web::ContextFeatureFlags kWebRunnerFeatures =
       fuchsia::web::ContextFeatureFlags::NETWORK |
       fuchsia::web::ContextFeatureFlags::AUDIO |
       fuchsia::web::ContextFeatureFlags::VULKAN |
       fuchsia::web::ContextFeatureFlags::HARDWARE_VIDEO_DECODER |
       fuchsia::web::ContextFeatureFlags::WIDEVINE_CDM;
 
-  // Vulkan is not currently available in our integration test environment.
-  DisableVulkanIfUnavailable(&features);
-
   WebContentRunner runner(
       base::fuchsia::ComponentContextForCurrentProcess()->outgoing().get(),
-      base::BindOnce(&WebContentRunner::CreateDefaultWebContext, features));
+      base::BindOnce(&WebContentRunner::CreateDefaultWebContext,
+                     kWebRunnerFeatures));
 
   base::fuchsia::ComponentContextForCurrentProcess()
       ->outgoing()