Initial commit for enhanced protection message in interstitials.

The goal is to replace the current SBER checkbox with this new enhanced
protection message whenever the user is able to opt-in to enhanced
protection. It applies to SAFEBROWSING, SSL and CAPTIVE_PORTAL
interstitials.

Adds a section named enhanced-protection-message in
interstitial_large.html, and adds a new command named
CMD_OPEN_ENHANCED_PROTECTION_SETTINGS in interstitial_commands.mojom to
handle the callback from js to c++.

Screenshot: http://screen/5AirLStp39i24Gm. To follow the mocks, an icon
and a different background color will be added in a future CL.

Also adds a chrome flag named
safe-browsing-enhanced-protection-message-in-interstitials to control
this feature.

Bug: 1130721,1130745
Change-Id: Ic5924ae2324a5fed1760b5549cb915c3279f1dbd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2427548
Commit-Queue: Xinghui Lu <[email protected]>
Reviewed-by: Yaron Friedman <[email protected]>
Reviewed-by: Varun Khaneja <[email protected]>
Reviewed-by: Emily Stark <[email protected]>
Cr-Commit-Position: refs/heads/master@{#812960}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 97c25e7..1fa701f 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1160,6 +1160,10 @@
 extern const char kPrinterStatusDialogName[];
 extern const char kPrinterStatusDialogDescription[];
 
+extern const char kSafeBrowsingEnhancedProtectionMessageInInterstitialsName[];
+extern const char
+    kSafeBrowsingEnhancedProtectionMessageInInterstitialsDescription[];
+
 extern const char kSafetyTipName[];
 extern const char kSafetyTipDescription[];