Add ability to wire up sharelist in glcontext creation

include/gpu/gl/SkGLContext.h

 
 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkGLContext_DEFINED
 #define SkGLContext_DEFINED
 
@@ skipping 95 matching lines @@
     SkPlatformGpuFence            fFrameFences[kMaxFrameLag - 1];
     int                           fCurrentFenceIdx;
 
     /** Subclass provides the gl interface object if construction was
      *  successful. */
     SkAutoTUnref<const GrGLInterface> fGL;
 
     friend class GLFenceSync;  // For onPlatformGetProcAddress.
 };
 
-/** Creates platform-dependent GL context object
- * Returns a valid gl context object or NULL if such can not be created.
- * Note: If Skia embedder needs a custom GL context that sets up the GL
- * interface, this function should be implemented by the embedder.
- * Otherwise, the default implementation for the platform should be compiled in
- * the library.
+/** Creates platform-dependent GL context object.  The shareContext parameter is in an optional
+ * context with which to share display lists. This should be a pointer to an SkGLContext created
+ * with SkCreatePlatformGLContext.  NULL indicates that no sharing is to take place. Returns a valid
+ * gl context object or NULL if such can not be created.
+ * Note: If Skia embedder needs a custom GL context that sets up the GL interface, this function
+ * should be implemented by the embedder. Otherwise, the default implementation for the platform
+ * should be compiled in the library.
  */
-SK_API SkGLContext* SkCreatePlatformGLContext(GrGLStandard forcedGpuAPI);
+SK_API SkGLContext* SkCreatePlatformGLContext(GrGLStandard forcedGpuAPI,
+                                              SkGLContext* shareContext = nullptr);
 
 /**
  * Helper macros for using the GL context through the GrGLInterface. Example:
  * SK_GL(glCtx, GenTextures(1, &texID));
  */
 #define SK_GL(ctx, X) (ctx).gl()->fFunctions.f ## X;    \
                       SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X;    \
                   SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->fFunctions.f ## X
 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X
 
 #endif