Fix wrong header guards found by clang's new Wheader-guard.

Fix wrong header guards found by clang's new Wheader-guard.

Example diagnostic:

In file included from ../../ppapi/tests/test_flash_file.cc:5:
../../ppapi/tests/test_flash_file.h:5:9: error: 'PAPPI_TESTS_TEST_FLASH_FILE_H_' is used as a header guard here, followed by #define of a different macro [-Werror,-Wheader-guard]

        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../ppapi/tests/test_flash_file.h:6:9: note: 'PPAPI_TESTS_TEST_FLASH_FILE_H_' is defined here; did you mean 'PAPPI_TESTS_TEST_FLASH_FILE_H_'?

        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        PAPPI_TESTS_TEST_FLASH_FILE_H_
1 error generated.

BUG=none
R=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=206837

[Nico, 2013-06-17 21:46:26]

Hi Ben,

can I get a toplevel lg for this? Then I don't have to hunt down a bunch of
owners for what is a trivial change.

Thanks!

[Ben Goodger (Google), 2013-06-17 22:14:30]

lgtm

[commit-bot: I haz the power, 2013-06-17 22:17:13]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/17321002/2001

[Nico, 2013-06-17 23:48:54]

Committed patchset #2 manually as r206837 (presubmit successful).