Allow WebGL readback for Mesa llvmpipe driver

gpu/config/gpu_info_collector.cc

Index: gpu/config/gpu_info_collector.cc
diff --git a/gpu/config/gpu_info_collector.cc b/gpu/config/gpu_info_collector.cc
index 44df9f1550b2b73ed58c3bc6b994130cbaca8498..e24e93d3a79c6c05977c91aa2ce2e1b34a70d086 100644
--- a/gpu/config/gpu_info_collector.cc
+++ b/gpu/config/gpu_info_collector.cc
@@ -10,6 +10,7 @@
 #include <string>
 #include <vector>
 
+#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/sparse_histogram.h"
@@ -18,6 +19,7 @@
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/trace_event/trace_event.h"
+#include "gpu/config/gpu_switches.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_implementation.h"
@@ -118,8 +120,23 @@ CollectInfoResult CollectGraphicsInfoGL(GPUInfo* gpu_info) {
 
   gpu_info->gl_renderer = GetGLString(GL_RENDERER);
   gpu_info->gl_vendor = GetGLString(GL_VENDOR);
-  gpu_info->gl_extensions = gfx::GetGLExtensionsFromCurrentContext();
   gpu_info->gl_version = GetGLString(GL_VERSION);
+
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kGpuTestingGLVendor)) {
+    gpu_info->gl_vendor =
+        command_line->GetSwitchValueASCII(switches::kGpuTestingGLVendor);
+  }
+  if (command_line->HasSwitch(switches::kGpuTestingGLRenderer)) {
+    gpu_info->gl_renderer =
+        command_line->GetSwitchValueASCII(switches::kGpuTestingGLRenderer);
+  }
+  if (command_line->HasSwitch(switches::kGpuTestingGLVersion)) {
+    gpu_info->gl_version =
+        command_line->GetSwitchValueASCII(switches::kGpuTestingGLVersion);
+  }
+
+  gpu_info->gl_extensions = gfx::GetGLExtensionsFromCurrentContext();
   std::string glsl_version_string = GetGLString(GL_SHADING_LANGUAGE_VERSION);
 
   gfx::GLVersionInfo gl_info(gpu_info->gl_version.c_str(),