ANGLETest: swap after resizing the window, before running the test.

This allows the test code to assume that the framebuffer size is equal
to the window size.

BUG=angleproject:1050

Change-Id: Ia4928d7a1d6cddb1ae330846bb44576db6a37533
Reviewed-on: https://chromium-review.googlesource.com/286253
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/tests/test_utils/ANGLETest.cpp b/src/tests/test_utils/ANGLETest.cpp
index 4e3e7db..dad58f0 100644
--- a/src/tests/test_utils/ANGLETest.cpp
+++ b/src/tests/test_utils/ANGLETest.cpp
@@ -24,6 +24,11 @@
     {
         FAIL() << "egl context creation failed.";
     }
+
+    // Swap the buffers so that the default framebuffer picks up the resize
+    // which will allow follow-up test code to assume the framebuffer covers
+    // the whole window.
+    swapBuffers();
 }
 
 void ANGLETest::TearDown()