Add swapBuffer call to SkGLContextHelper.

src/gpu/gl/android/SkNativeGLContext_android.cpp

Index: src/gpu/gl/android/SkNativeGLContext_android.cpp
diff --git a/src/gpu/gl/android/SkNativeGLContext_android.cpp b/src/gpu/gl/android/SkNativeGLContext_android.cpp
index 8811ddae9d2a29e25f76d89cdded70af286bf191..dda7d9d3fa03e09891566c88ac20894fde17e21c 100644
--- a/src/gpu/gl/android/SkNativeGLContext_android.cpp
+++ b/src/gpu/gl/android/SkNativeGLContext_android.cpp
@@ -165,3 +165,9 @@ void SkNativeGLContext::makeCurrent() const {
         SkDebugf("Could not set the context.\n");
     }
 }
+
+void SkNativeGLContext::swapBuffers() const {
+    if (!eglSwapBuffers(fDisplay, fSurface)) {
+        SkDebugf("Could not complete eglSwapBuffers.\n");
+    }
+}