Added switch to disable specified GL extensions.

ui/gl/gl_gl_api_implementation.cc

Index: ui/gl/gl_gl_api_implementation.cc
diff --git a/ui/gl/gl_gl_api_implementation.cc b/ui/gl/gl_gl_api_implementation.cc
index 6752a25ee5a83644a00495804ffb027d81a54859..81e6c1bf51283d9d9d56816b54cb35dce7885484 100644
--- a/ui/gl/gl_gl_api_implementation.cc
+++ b/ui/gl/gl_gl_api_implementation.cc
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "base/command_line.h"
+#include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_implementation.h"
@@ -398,6 +399,44 @@ void GLApiBase::InitializeBase(DriverGL* driver) {
 }
 
 RealGLApi::RealGLApi() {

[no sievers, 2015/04/30 20:45:02]

That doesn't work. |driver_| will be NULL when RealGLApi is constructed and your
GL calls below will crash.
Can you simply move it to Initialize()?

[David Yen, 2015/04/30 22:14:17]

Done.

+  const base::CommandLine* cmd_line = base::CommandLine::ForCurrentProcess();
+  const std::string disabled_extensions = cmd_line->GetSwitchValueASCII(
+      switches::kDisableGLExtensions);
+  if (!disabled_extensions.empty()) {
+    std::vector<std::string> disabled_extensions_vec;
+    Tokenize(disabled_extensions, ", ;", &disabled_extensions_vec);
+
+    // Fill in filtered_exts_ vector first.
+    if (gfx::GetGLImplementation() !=
+        gfx::kGLImplementationDesktopGLCoreProfile) {
+      const char* gl_extensions = reinterpret_cast<const char*>(
+          GLApiBase::glGetStringFn(GL_EXTENSIONS));
+      if (gl_extensions)
+        base::SplitString(gl_extensions, ' ', &filtered_exts_);
+    } else {
+      GLint num_extensions = 0;
+      GLApiBase::glGetIntegervFn(GL_NUM_EXTENSIONS, &num_extensions);
+      for (GLint i = 0; i < num_extensions; ++i) {
+        const char* gl_extension = reinterpret_cast<const char*>(
+            GLApiBase::glGetStringiFn(GL_EXTENSIONS, i));
+        DCHECK(gl_extension != NULL);
+        filtered_exts_.push_back(gl_extension);
+      }
+    }
+
+    // Filter out extensions from the command line.
+    for (const std::string& disabled_ext : disabled_extensions_vec) {
+      filtered_exts_.erase(std::remove(filtered_exts_.begin(),

[no sievers, 2015/04/30 20:45:02]

Actually can you just use std::set<> instead of vector<> then and do
std::set_difference here?

+                                       filtered_exts_.end(),
+                                       disabled_ext),
+                           filtered_exts_.end());
+    }
+
+    // Construct filtered extensions string for GL_EXTENSIONS string lookups.
+    filtered_exts_str_ = JoinString(filtered_exts_, " ");
+
+    extensions_filtered_ = true;

[no sievers, 2015/04/30 20:45:02]

Why do we need this?
It seems like it would just cause a bug if something below got the unfiltered
string. And above you are calling GLApiBase directly.

[David Yen, 2015/04/30 22:14:17]

This was originally added to fix the mock interface expectations, it expects the
GLApiBase::glGet...Fn() to be called so we cannot do our filtering for unit
tests. It should only be false if we are not filtering anything.

+  }
 }
 
 RealGLApi::~RealGLApi() {
@@ -407,6 +446,31 @@ void RealGLApi::Initialize(DriverGL* driver) {
   InitializeBase(driver);
 }
 
+void RealGLApi::glGetIntegervFn(GLenum pname, GLint* params) {
+  if (extensions_filtered_ && pname == GL_NUM_EXTENSIONS) {
+    *params = static_cast<GLint>(filtered_exts_str_.size());

[Zhenyao Mo, 2015/04/29 20:04:23]

This is incorrect. I think you mean filtered_ext_.size() instead.

[David Yen, 2015/04/30 22:14:17]

Ah good catch, Done.

+  } else {
+    GLApiBase::glGetIntegervFn(pname, params);
+  }
+}
+
+const GLubyte* RealGLApi::glGetStringFn(GLenum name) {
+  if (extensions_filtered_ && name == GL_EXTENSIONS) {
+    return reinterpret_cast<const GLubyte*>(filtered_exts_str_.c_str());
+  }
+  return GLApiBase::glGetStringFn(name);
+}
+
+const GLubyte* RealGLApi::glGetStringiFn(GLenum name, GLuint index) {
+  if (extensions_filtered_ && name == GL_EXTENSIONS) {
+    if (index >= filtered_exts_.size()) {
+      return NULL;
+    }
+    return reinterpret_cast<const GLubyte*>(filtered_exts_[index].c_str());
+  }
+  return GLApiBase::glGetStringiFn(name, index);
+}
+
 void RealGLApi::glFlushFn() {
   GLApiBase::glFlushFn();
 }