[cros] Fix two issues related to gtk im context support.

[cros] Fix two issues related to gtk im context support.

BUG=chromium-os:9208
BUG=chromium-os:9575
TEST=See bug reports.

Issue 9208 is due to ibus's async nature: some ibus engines may update preedit string when getting reset. It may happen after calling GtkIMContextWrapper::CancelComposition() method, which then cause this method being called recursively.
So we need to suppress any preedit string signals triggered by GtkIMContextWrapper::CancelComposition() method, just like what we have done for commit signal (http://crbug.com/50485 and issue http://crosbug.com/4792).

Issue 9575 is caused by improper handling of "grab-notify" signal in RWHVGtk, which should not focus in the input context again when the window has been focused out.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=67207

[satorux1, 2010-11-24 01:56:02]

LGTM. Thank you for fixing the important bugs. Can you merge this to 552d?

http://codereview.chromium.org/5372001/diff/1/chrome/browser/renderer_host/gt...
File chrome/browser/renderer_host/gtk_im_context_wrapper.cc (right):

http://codereview.chromium.org/5372001/diff/1/chrome/browser/renderer_host/gt...
chrome/browser/renderer_host/gtk_im_context_wrapper.cc:459: if
(!suppress_next_commit_)
You might want to make the code look like line 466-468, for consistency:

if (suppress_next_commit_)
  return;