Fix regression --use-gl=egl does not select Mesa anymore

Instead it always selects angle, like if --use-gl=angle was set
which makes --use-gl=egl useless.

My understanding is that --use-gl=egl is supposed to select
the defaults libEGL.so.1/libGLESv2.so.2 available on the system.

Regression introduced by 06a905b5
"Fixed fallback to software for tests"
https://chromium-review.googlesource.com/517912

BUG=726075

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Idf3cfb1b5480a112f73b7e7c20f4d4ade1cc2a51
Reviewed-on: https://chromium-review.googlesource.com/690074Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Julien Isorce <julien.isorce@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505331}

ui/gl/init/gl_factory.cc

@@ -24,7 +24,7 @@ bool InitializeGLOneOffHelper(bool init_extensions) {
   std::vector<GLImplementation> allowed_impls = GetAllowedGLImplementations();
   DCHECK(!allowed_impls.empty());
 
-  base::CommandLine* cmd = base::CommandLine::ForCurrentProcess();
+  const base::CommandLine* cmd = base::CommandLine::ForCurrentProcess();
 
   // The default implementation is always the first one in list.
   GLImplementation impl = allowed_impls[0];

ui/gl/init/gl_initializer_x11.cc

@@ -85,6 +85,8 @@ bool InitializeStaticEGLInternal(GLImplementation implementation) {
   base::FilePath glesv2_path(kGLESv2LibraryName);
   base::FilePath egl_path(kEGLLibraryName);
 
+  const base::CommandLine* cmd = base::CommandLine::ForCurrentProcess();
+
   if (implementation == kGLImplementationSwiftShaderGL) {
 #if BUILDFLAG(ENABLE_SWIFTSHADER)
     base::FilePath module_path;
@@ -97,7 +99,8 @@ bool InitializeStaticEGLInternal(GLImplementation implementation) {
 #else
     return false;
 #endif
-  } else {
+  } else if (cmd->GetSwitchValueASCII(switches::kUseGL) ==
+             kGLImplementationANGLEName) {
     base::FilePath module_path;
     if (!PathService::Get(base::DIR_MODULE, &module_path))
       return false;