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 /ui/gfx/canvas_skia.cc

This CL was uploaded by git cl split.

R=danakj@chromium.org

Bug: 1110266
Change-Id: I791bd924bc12bc017b8708ecfa8b7ac33d32b005
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2370735
Auto-Submit: Sean McAllister <smcallis@google.com>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801141}

ui/gfx/canvas_skia.cc

@@ -206,7 +206,7 @@ void Canvas::DrawStringRectWithFlags(const base::string16& text,
     Range range = StripAcceleratorChars(flags, &adjusted_text);
     bool elide_text = ((flags & NO_ELLIPSIS) == 0);
 
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
     // On Linux, eliding really means fading the end of the string. But only
     // for LTR text. RTL text is still elided (on the left) with "...".
     if (elide_text) {