Use lowercase windows.h in includes to fix Windows cross compilation using mingw.

src/gpu/gl/win/SkNativeGLContext_win.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gl/SkNativeGLContext.h"
 #include "SkWGL.h"
 
 #define WIN32_LEAN_AND_MEAN
-#include <Windows.h>
+#include <windows.h>
 
 SkNativeGLContext::AutoContextRestore::AutoContextRestore() {
     fOldHGLRC = wglGetCurrentContext();
     fOldHDC = wglGetCurrentDC();
 }
 
 SkNativeGLContext::AutoContextRestore::~AutoContextRestore() {
     wglMakeCurrent(fOldHDC, fOldHGLRC);
 }
 
@@ skipping 87 matching lines @@
     if (!wglMakeCurrent(fDeviceContext, fGlRenderContext)) {
         SkDebugf("Could not create rendering context.\n");
     }
 }
 
 void SkNativeGLContext::swapBuffers() const {
     if (!SwapBuffers(fDeviceContext)) {
         SkDebugf("Could not complete SwapBuffers.\n");
     }
 }