Change GLGetProcAddress typedef to function returning function pointer

ui/gl/gl_implementation.h

 // Copyright (c) 2012 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 UI_GL_GL_IMPLEMENTATION_H_
 #define UI_GL_GL_IMPLEMENTATION_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 17 matching lines @@
 };
 
 struct GL_EXPORT GLWindowSystemBindingInfo {
   GLWindowSystemBindingInfo();
   std::string vendor;
   std::string version;
   std::string extensions;
   bool direct_rendering;
 };
 
+using GLFunctionPointerType = void (*)();

[Ken Russell (switch to Gerrit), 2016/12/21 16:45:17]

Is it OK that this "using" statement doesn't include the calling convention
WINAPI on Windows platforms? Given that everything compiles and passes tests I
assume it is, but the GL headers all use that specifier on the function pointers
they define.

 #if defined(OS_WIN)
-typedef void* (WINAPI *GLGetProcAddressProc)(const char* name);
+typedef GLFunctionPointerType(WINAPI* GLGetProcAddressProc)(const char* name);
 #else
-typedef void* (*GLGetProcAddressProc)(const char* name);
+typedef GLFunctionPointerType (*GLGetProcAddressProc)(const char* name);
 #endif
 
 // Initialize stub methods for drawing operations in the GL bindings. The
 // null draw bindings default to enabled, so that draw operations do nothing.
 GL_EXPORT void InitializeNullDrawGLBindings();
 
 // TODO(danakj): Remove this when all test suites are using null-draw.
 GL_EXPORT bool HasInitializedNullDrawGLBindings();
 
 // Filter a list of disabled_extensions from GL style space-separated
@@ skipping 40 matching lines @@
 // Exported so that tests may set the function used in the mock implementation.
 GL_EXPORT void SetGLGetProcAddressProc(GLGetProcAddressProc proc);
 
 // Find an entry point in the current GL implementation. Note that the function
 // may return a non-null pointer to something else than the GL function if an
 // unsupported function is queried. Spec-compliant eglGetProcAddress and
 // glxGetProcAddress are allowed to return garbage for unsupported functions,
 // and when querying functions from the EGL library supplied by Android, it may
 // return a function that prints a log message about the function being
 // unsupported.
-GL_EXPORT void* GetGLProcAddress(const char* name);
+GL_EXPORT GLFunctionPointerType GetGLProcAddress(const char* name);
 
 // Helper for fetching the OpenGL extensions from the current context.
 // This helper abstracts over differences between the desktop OpenGL
 // core profile, and OpenGL ES and the compatibility profile.  It's
 // intended for users of the bindings, not the implementation of the
 // bindings themselves. This is a relatively expensive call, so
 // callers should cache the result.
 GL_EXPORT std::string GetGLExtensionsFromCurrentContext();
 
 // Helper for the GL bindings implementation to understand whether
 // glGetString(GL_EXTENSIONS) or glGetStringi(GL_EXTENSIONS, i) will
 // be used in the function above.
 GL_EXPORT bool WillUseGLGetStringForExtensions();
 
 // Helpers to load a library and log error on failure.
 GL_EXPORT base::NativeLibrary LoadLibraryAndPrintError(
     const base::FilePath::CharType* filename);
 GL_EXPORT base::NativeLibrary LoadLibraryAndPrintError(
     const base::FilePath& filename);
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_IMPLEMENTATION_H_