[ios] Add strings for grid tabs use when incognito policy is set

This cl add strings which will be used by grid tabs when
IncognitoModeAvailability policy is set to disabled/force.
Mock: https://docs.google.com/presentation/d/19BYpNAMopjUnxVdI3Gc4WcpJ6IVAZ_kw_4CCNs3tP3A/edit#slide=id.g5412b41971_0_147

Submit this cl first because it contains string changes.

The follow up cls are:
1. Create empty tab grid with enterprise message for normal tab grid,
incognito tab grid and the recent tabs grid.
2. Prevent the access to certain tab grid and using empty tab grid when
incognito mode is disabled/forced.
3. Add click action on the "learn more" in-text link.
4. Disable new tab button in certain mode.

Bug: 1148888

Change-Id: I8ba847935ed0228b45c0125f7f2d590e276daa3d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2595591
Commit-Queue: Tina Wang <tinazwang@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838243}

ios/chrome/app/strings/ios_strings.grd

@@ -2330,6 +2330,18 @@ Your data was encrypted with your sync passphrase on <ph name="TIME">$2<ex>Sept
       <message name="IDS_IOS_TAB_GRID_INCOGNITO_TABS_EMPTY_TITLE" desc="Title shown above a message on the incognito tab switcher when there are no incognito tabs. [iOS only]">
         You'll find your Incognito tabs here
       </message>
+      <message name="IDS_IOS_TAB_GRID_INCOGNITO_TABS_UNAVAILABLE_MESSAGE" desc="Message shown in the Incognito Tabs page of the tab grid when the IncognitoModeAvailability enterprise policy is set to disabled. [iOS only]">
+        Your organization turned off private browsing. <ph name="BEGIN_LINK">BEGIN_LINK</ph>Learn more<ph name="END_LINK">END_LINK</ph>
+      </message>
+      <message name="IDS_IOS_TAB_GRID_INCOGNITO_TABS_UNAVAILABLE_TITLE" desc="Title shown above a message in the Incognito Tabs page of the tab grid when the IncognitoModeAvailability enterprise policy is set to disabled. [iOS only]">
+        Incognito Mode is Unavailable
+      </message>
+      <message name="IDS_IOS_TAB_GRID_RECENT_TABS_UNAVAILABLE_MESSAGE" desc="Message shown in the Recent Tabs page of the tab grid when the IncognitoModeAvailability enterprise policy is set to forced. [iOS only]">
+        Your organization requires you to browse privately. Tabs aren't saved in Incognito mode. <ph name="BEGIN_LINK">BEGIN_LINK</ph>Learn more<ph name="END_LINK">END_LINK</ph>
+      </message>
+      <message name="IDS_IOS_TAB_GRID_RECENT_TABS_UNAVAILABLE_TITLE" desc="Title shown above a message in the Recent Tabs page of the tab grid when the IncognitoModeAvailability enterprise policy is set to forced. [iOS only]">
+        Recent Tabs are Unavailable
+      </message>
       <message name="IDS_IOS_TAB_GRID_REGULAR_TABS_EMPTY_STATE_TITLE" desc="Title shown in the Regular Tabs page (as opposed to the Incognito Tabs page) when the grid is empty. [iOS only]">
         No Open Tabs
       </message>
@@ -2345,6 +2357,12 @@ Your data was encrypted with your sync passphrase on <ph name="TIME">$2<ex>Sept
       <message name="IDS_IOS_TAB_GRID_REGULAR_TABS_EMPTY_MESSAGE" desc="Message shown underneath a title on the regular tab switcher when there are no tabs, explaining why to use the regular tab switcher. [iOS only]">
         Open tabs to visit different pages at the same time
       </message>
+      <message name="IDS_IOS_TAB_GRID_REGULAR_TABS_UNAVAILABLE_MESSAGE" desc="Message shown in the Regular Tabs page of the tab grid when the IncognitoModeAvailability enterprise policy is set to forced. [iOS only]">
+        Your organization requires you to browse privately. <ph name="BEGIN_LINK">BEGIN_LINK</ph>Learn more<ph name="END_LINK">END_LINK</ph>
+      </message>
+      <message name="IDS_IOS_TAB_GRID_REGULAR_TABS_UNAVAILABLE_TITLE" desc="Title shown above a message in the Regular Tabs page of the tab grid when the IncognitoModeAvailability enterprise policy is set to forced. [iOS only]">
+        Only Incognito Mode is Available
+      </message>
       <message name="IDS_IOS_TAB_GRID_CREATE_NEW_INCOGNITO_TAB" desc="The accessibility label for the button that creates new incognito tabs. [iOS only]">
         Create new incognito tab.
       </message>

ios/chrome/app/strings/ios_strings_grd/IDS_IOS_TAB_GRID_INCOGNITO_TABS_UNAVAILABLE_MESSAGE.png.sha1

+fe6825ceac5003ce617dffa5601b32e1c330fd27
\ No newline at end of file

ios/chrome/app/strings/ios_strings_grd/IDS_IOS_TAB_GRID_INCOGNITO_TABS_UNAVAILABLE_TITLE.png.sha1

+8baa7028337b30506a7e4fa9b60355870e0048d6
\ No newline at end of file

ios/chrome/app/strings/ios_strings_grd/IDS_IOS_TAB_GRID_RECENT_TABS_UNAVAILABLE_MESSAGE.png.sha1

+5c261cec0cd219677f6e4e9d6f660d082951c6b4
\ No newline at end of file

ios/chrome/app/strings/ios_strings_grd/IDS_IOS_TAB_GRID_RECENT_TABS_UNAVAILABLE_TITLE.png.sha1

+31de1cbb899faa1b47c4476bb7d62b102656d4ab
\ No newline at end of file

ios/chrome/app/strings/ios_strings_grd/IDS_IOS_TAB_GRID_REGULAR_TABS_UNAVAILABLE_MESSAGE.png.sha1

+bb7821a31452dae47c50fdb6c32371e7e4aa9dfa
\ No newline at end of file

ios/chrome/app/strings/ios_strings_grd/IDS_IOS_TAB_GRID_REGULAR_TABS_UNAVAILABLE_TITLE.png.sha1

+eac9f509403b34bea25b03d710df4db7b5b36fa3
\ No newline at end of file