Replace std::map with base::flat_map in safe browsing services_delegate

Pros: Good memory locality, low overhead especially for smaller maps.
Cons: Inserts and removals are O(n). But since the keys are profiles,
there shouldn't be too many insert and remove operations.

Bug: 995926
Change-Id: I2b26d5ebeba3c12732c3ad71a772afaa0262cf08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1845577Reviewed-by: Varun Khaneja <vakh@chromium.org>
Commit-Queue: Xinghui Lu <xinghuilu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703801}

chrome/browser/safe_browsing/services_delegate.h

@@ -148,16 +148,16 @@ class ServicesDelegate {
   // Unowned pointer
   ServicesCreator* const services_creator_;
 
-  // TODO(xinghuilu@): Change it to base::map<>
   // Tracks existing Profiles, and their corresponding
   // ChromePasswordProtectionService instances.
   // Accessed on UI thread.
-  std::map<Profile*, std::unique_ptr<ChromePasswordProtectionService>>
+  base::flat_map<Profile*, std::unique_ptr<ChromePasswordProtectionService>>
       password_protection_service_map_;
 
   // Tracks existing Profiles, and their corresponding VerdictCacheManager
   // instances. Accessed on UI thread.
-  std::map<Profile*, std::unique_ptr<VerdictCacheManager>> cache_manager_map_;
+  base::flat_map<Profile*, std::unique_ptr<VerdictCacheManager>>
+      cache_manager_map_;
 };
 
 }  // namespace safe_browsing