skia: Add support for ANGLE on linux

src/gpu/gl/angle/GrGLCreateANGLEInterface.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "gl/GrGLInterface.h"
 #include "gl/GrGLAssembleInterface.h"
 
+#if defined _WIN32
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
+#else
+#include <dlfcn.h>
+#endif // defined _WIN32
+
 #include <EGL/egl.h>
 
 static GrGLFuncPtr angle_get_gl_proc(void* ctx, const char name[]) {
+#if defined _WIN32
     GrGLFuncPtr proc = (GrGLFuncPtr) GetProcAddress((HMODULE)ctx, name);
+#else
+    GrGLFuncPtr proc = (GrGLFuncPtr) dlsym(ctx, name);
+#endif // defined _WIN32
     if (proc) {
         return proc;
     }
     return eglGetProcAddress(name);
 }
 
 const GrGLInterface* GrGLCreateANGLEInterface() {
+    static void* gANGLELib = nullptr;
 
-    static HMODULE ghANGLELib = nullptr;
+    if (nullptr == gANGLELib) {
+        // We load the ANGLE library and never let it go
+#if defined _WIN32
+        gANGLELib = LoadLibrary("libGLESv2.dll");
+#else
+        gANGLELib = dlopen("libGLESv2.so", RTLD_LAZY);
+#endif // defined _WIN32
+    }
 
-    if (nullptr == ghANGLELib) {
-        // We load the ANGLE library and never let it go
-        ghANGLELib = LoadLibrary("libGLESv2.dll");
-    }
-    if (nullptr == ghANGLELib) {
-        // We can't setup the interface correctly w/o the DLL
+    if (nullptr == gANGLELib) {
+        // We can't setup the interface correctly w/o the so
         return nullptr;
     }
 
-    return GrGLAssembleGLESInterface(ghANGLELib, angle_get_gl_proc);
+    return GrGLAssembleGLESInterface(gANGLELib, angle_get_gl_proc);
 }