Use a sample content settings patterns as placeholder string on the exceptions dialog

On Content Settings exceptions dialogs: Replace the placeholder text ("Add a new hostname pattern") of the input field used for adding new exceptions with a string containing a sample pattern ("[*.]example.com")

BUG=232378
TEST= (1) open chrome://settings/contentExceptions#cookies
  (2) Verify that the text in the input field is "[*.]example.com"

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=194592

[markusheintz_, 2013-04-17 14:22:17]

Dominic could you please review this CL ? Thanks a lot

[battre, 2013-04-17 14:27:06]

lgtm

[markusheintz_, 2013-04-17 15:01:37]

Committed patchset #2 manually as r194592 (presubmit successful).