Added an experiment for an LRU snapshot cache.

ios/chrome/browser/experimental_flags.h

Index: ios/chrome/browser/experimental_flags.h
diff --git a/ios/chrome/browser/experimental_flags.h b/ios/chrome/browser/experimental_flags.h
index 7f13f9e06df26d0d9fc1f2ed1ef35b35b5cdd43d..a284e187517c467efd35dc1efbed34a9b09c717f 100644
--- a/ios/chrome/browser/experimental_flags.h
+++ b/ios/chrome/browser/experimental_flags.h
@@ -23,6 +23,9 @@ bool IsBookmarkCollectionEnabled();
 // only whether the trial state will be checked in the default state.
 void SetWKWebViewTrialEligibility(bool eligible);
 
+// Whether the lru snapshot cache experiment is enabled.
+bool IsLRUSnapshotCacheEnabled();
+
 // Whether the app uses WKWebView instead of UIWebView.
 // The returned value will not change within a given session.
 bool IsWKWebViewEnabled();