Remove --enable-fixed-layout flag

This flag was removed long ago in https://crrev.com/35503005 but remains
as a flag in the Android virtual test suite. This patch removes it, it
should be a no-op.

Bug: 285397
Change-Id: I5e99d279e96baea3b495150f19b4e52a193a92d1
Reviewed-on: https://chromium-review.googlesource.com/562926
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486178}

third_party/WebKit/LayoutTests/VirtualTestSuites

@@ -174,8 +174,7 @@
              "--enable-fixed-position-compositing", "--enable-prefer-compositing-to-lcd-text",
              "--enable-composited-scrolling-for-frames", "--enable-gesture-tap-highlight", "--enable-pinch",
              "--force-overlay-fullscreen-video", "--enable-overscroll-notifications",
-             "--enable-fixed-layout", "--enable-viewport", "--disable-canvas-aa",
-             "--disable-composited-antialiasing"]
+             "--enable-viewport", "--disable-canvas-aa", "--disable-composited-antialiasing"]
   },
   {
     "prefix": "android",
@@ -184,8 +183,7 @@
              "--enable-fixed-position-compositing", "--enable-prefer-compositing-to-lcd-text",
              "--enable-composited-scrolling-for-frames", "--enable-gesture-tap-highlight", "--enable-pinch",
              "--force-overlay-fullscreen-video", "--enable-overscroll-notifications",
-             "--enable-fixed-layout", "--enable-viewport", "--disable-canvas-aa",
-             "--disable-composited-antialiasing"]
+             "--enable-viewport", "--disable-canvas-aa", "--disable-composited-antialiasing"]
   },
   {
     "prefix": "media-gpu-accelerated",