Add Mesa as a GL backend.
http://codereview.appspot.com/4545055/


git-svn-id: http://skia.googlecode.com/svn/trunk@1382 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/utils/SkEGLContext.h b/include/utils/SkEGLContext.h
index 6aa8518..d67cf0c 100644
--- a/include/utils/SkEGLContext.h
+++ b/include/utils/SkEGLContext.h
@@ -1,7 +1,9 @@
 #ifndef SkEGLContext_DEFINED
 #define SkEGLContext_DEFINED
 
-#if defined(SK_BUILD_FOR_MAC)
+#if defined(SK_MESA)
+    #include "GL/osmesa.h"
+#elif defined(SK_BUILD_FOR_MAC)
     #include <AGL/agl.h>
 #elif defined(SK_BUILD_FOR_UNIX)
     #include <X11/Xlib.h>
@@ -18,10 +20,13 @@
     SkEGLContext();
     ~SkEGLContext();
 
-    bool init(int width, int height);
+    bool init(const int width, const int height);
 
 private:
-#if defined(SK_BUILD_FOR_MAC)
+#if defined(SK_MESA)
+    OSMesaContext context;
+    GLfloat *image;
+#elif defined(SK_BUILD_FOR_MAC)
     AGLContext context;
 #elif defined(SK_BUILD_FOR_UNIX)
     GLXContext context;