Refactor OS_LINUX preprocessor directive for LaCrOS effort.

Currently, ChromeOS defines the OS_LINUX directive as well as
OS_CHROMEOS.  We're working to separate these two, so we're
making the fact that OS_LINUX == OS_LINUX || OS_CHROMEOS
explicit.

This is changes for /chrome/browser/media/webrtc/webrtc_event_log_uploader.cc

This CL was uploaded by git cl split.

R=eladalon@chromium.org

Bug: 1110266
Change-Id: Ia97f38c0618c485c91dcd8dc60368eaa130cf699
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2371249Reviewed-by: Elad Alon <eladalon@chromium.org>
Commit-Queue: Sean McAllister <smcallis@google.com>
Cr-Commit-Position: refs/heads/master@{#801928}

chrome/browser/media/webrtc/webrtc_event_log_uploader.cc

@@ -36,12 +36,12 @@ constexpr size_t kExpectedMimeOverheadBytes = 1000;  // Intentional overshot.
 const char kProduct[] = "Chrome";
 #elif defined(OS_MAC)
 const char kProduct[] = "Chrome_Mac";
+#elif defined(OS_CHROMEOS)
+const char kProduct[] = "Chrome_ChromeOS";
 #elif defined(OS_LINUX)
 const char kProduct[] = "Chrome_Linux";
 #elif defined(OS_ANDROID)
 const char kProduct[] = "Chrome_Android";
-#elif defined(OS_CHROMEOS)
-const char kProduct[] = "Chrome_ChromeOS";
 #else
 #error Platform not supported.
 #endif