[bfcache] Fix chrome://flags entry for bfcache

Fix chrome://flags behaviour for bfcache flag forcing caching:
- Ensure that all parameters are correctly captured
- Rename the mode to "Force caching all pages" to be more clear
- Extend timeout to 1 hour for easier testing.

R=carlscab@google.com

Change-Id: I7df177abccea0fa849a5834c13b75464553c5cfb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1919759
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#715897}

chrome/browser/about_flags.cc

@@ -1367,14 +1367,13 @@ const FeatureEntry::FeatureVariation kQuietNotificationPromptsVariations[] = {
 
 // TODO(crbug.com/991082,1015377): Remove after proper support for back-forward
 // cache is implemented.
-const FeatureEntry::FeatureParam kBackForwardCache_ExtendedSupport[] = {
-    {"service_worker_supported", "true"},
-    {"geolocation_supported", "true"},
+const FeatureEntry::FeatureParam kBackForwardCache_ForceCaching[] = {
+    {"TimeToLiveInBackForwardCacheInSeconds", "300"},
     {"should_ignore_blocklists", "true"}};
 
 const FeatureEntry::FeatureVariation kBackForwardCacheVariations[] = {
-    {"experimental extended supported feature set",
-     kBackForwardCache_ExtendedSupport, 1, nullptr},
+    {"force caching all pages", kBackForwardCache_ForceCaching,
+     base::size(kBackForwardCache_ForceCaching), nullptr},
 };
 
 #if defined(OS_CHROMEOS)