Enable SwiftShader fallback on desktop Linux.

content/browser/gpu/gpu_data_manager_impl_private.cc

 // Copyright (c) 2013 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 "content/browser/gpu/gpu_data_manager_impl_private.h"
 
 #include <algorithm>
 #include <iterator>
 #include <memory>
 #include <utility>
@@ skipping 373 matching lines @@
     std::set<int> feature_diffs;
     std::set_difference(blacklisted_features_.begin(),
                         blacklisted_features_.end(),
                         preliminary_blacklisted_features_.begin(),
                         preliminary_blacklisted_features_.end(),
                         std::inserter(feature_diffs, feature_diffs.begin()));
     if (feature_diffs.size()) {
       // TODO(zmo): Other features might also be OK to ignore here.
       feature_diffs.erase(gpu::GPU_FEATURE_TYPE_ACCELERATED_WEBGL);
       feature_diffs.erase(gpu::GPU_FEATURE_TYPE_WEBGL2);
+      feature_diffs.erase(gpu::GPU_FEATURE_TYPE_ACCELERATED_2D_CANVAS);
     }
     if (feature_diffs.size()) {
       if (reason) {
         *reason = "Features are disabled on full but not preliminary GPU info.";
       }
       return false;
     }
   }
 
   if (blacklisted_features_.size() == gpu::NUMBER_OF_GPU_FEATURE_TYPES) {
@@ skipping 860 matching lines @@
 }
 
 void GpuDataManagerImplPrivate::EnableSwiftShaderIfNecessary() {
 #if BUILDFLAG(ENABLE_SWIFTSHADER)
   if ((!GpuAccessAllowed(nullptr) ||
        blacklisted_features_.count(gpu::GPU_FEATURE_TYPE_ACCELERATED_WEBGL)) &&
       !base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableSoftwareRasterizer)) {
     use_swiftshader_ = true;
 
-    // Remove all previously recorded GPU info
-    gpu_info_ = gpu::GPUInfo();
-    // Set some basic info to identify the GPU as SwiftShader
+    // Adjust GPU info for SwiftShader. Most of this data only affects the
+    // chrome://gpu page, so it doesn't require querying the implementation.
+    // It is important to reset the video and image decode/encode capabilities,
+    // to prevent attempts to use them (crbug.com/702417).

[piman, 2017/04/10 23:58:55]

Could we add a method on GPUInfo to do these things? I worry that as fields are
added to that class, this function will not be maintained.

Also, could we have a test that verifies that the values returned by SwiftShader
are consistent with the values we hard-code here?

+    gpu_info_.driver_vendor = "Google Inc.";
+    gpu_info_.driver_version = "3.3.0.2";
+    gpu_info_.driver_date = "2017/04/07";
+    gpu_info_.pixel_shader_version = "3.0";
+    gpu_info_.vertex_shader_version = "3.0";
+    gpu_info_.max_msaa_samples = "4";
+    gpu_info_.gl_version = "OpenGL ES 2.0 SwiftShader";
     gpu_info_.gl_vendor = "Google Inc.";
     gpu_info_.gl_renderer = "Google SwiftShader";
+    gpu_info_.gl_extensions = "";
+    gpu_info_.gl_reset_notification_strategy = 0;
     gpu_info_.software_rendering = true;
+    gpu_info_.passthrough_cmd_decoder = false;
+    gpu_info_.supports_overlays = false;
+    gpu_info_.basic_info_state = gpu::kCollectInfoNone;
+    gpu_info_.context_info_state = gpu::kCollectInfoNone;

[piman, 2017/04/10 23:58:55]

nit: kCollectInfoSuccess for both of these, since we have effectively
"collected" the info (by hard-coding it), so we don't want to try to collect it
again.

+    gpu_info_.video_decode_accelerator_capabilities = {};
+    gpu_info_.video_encode_accelerator_supported_profiles = {};
+    gpu_info_.jpeg_decode_accelerator_supported = false;
+
+    gpu_info_.gpu.active = false;
+    for (auto& secondary_gpu : gpu_info_.secondary_gpus)
+      secondary_gpu.active = false;
 
     for (auto& status : gpu_feature_info_.status_values)
       status = gpu::kGpuFeatureStatusBlacklisted;
   }
 #endif
 }
 
 std::string GpuDataManagerImplPrivate::GetDomainFromURL(
     const GURL& url) const {
   // For the moment, we just use the host, or its IP address, as the
@@ skipping 100 matching lines @@
   gpu_info_.context_info_state = gpu::kCollectInfoFatalFailure;
 #if defined(OS_WIN)
   gpu_info_.dx_diagnostics_info_state = gpu::kCollectInfoFatalFailure;
 #endif
   complete_gpu_info_already_requested_ = true;
   // Some observers might be waiting.
   NotifyGpuInfoUpdate();
 }
 
 }  // namespace content