Surfacing chrome://flags to enable context menu performance info.

This also changes feature flag behavior so that the PerformanceHintsObserver is enabled when kContextMenuPerformanceInfo is enabled. Enabling the UI without enabling the Observer is not a scenario we're interested in.

Bug: 1040661
Change-Id: I4970534ad4b21127ef603955c2b22bb7f5ce40dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067690
Commit-Queue: Josh Simmons <[email protected]>
Reviewed-by: David Trainor <[email protected]>
Cr-Commit-Position: refs/heads/master@{#744360}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 0b8a6c6..578869a 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2302,6 +2302,10 @@
 const char kContextMenuCopyImageDescription[] =
     "Enable copying image to system clipboard via context menu.";
 
+const char kContextMenuPerformanceInfoName[] = "Context menu performance hints";
+const char kContextMenuPerformanceInfoDescription[] =
+    "Show link performance information in the context menu.";
+
 const char kContextualSearchDefinitionsName[] = "Contextual Search definitions";
 const char kContextualSearchDefinitionsDescription[] =
     "Enables touch-activated contextual definitions of words on a page to be "