Remove most of the code to create URLRequestContexts in src/chrome.

This code isn't needed anymore. There's still a lot of related code left; I'm stopping at this point to keep changes manageable to review.

Bug: 934009
Change-Id: Ibe2b5861fa45f0bd8e67f86aed1d52c256b2e0a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1640718
Reviewed-by: Matt Menke <[email protected]>
Reviewed-by: Reilly Grant <[email protected]>
Commit-Queue: John Abd-El-Malek <[email protected]>
Cr-Commit-Position: refs/heads/master@{#665704}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index e783e9a..921bc1e 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1082,4 +1082,7 @@
 
   // Added 5/2019.
   profile_prefs->ClearPref(kBookmarkAppCreationLaunchType);
+
+  // Added 6/2019.
+  profile_prefs->ClearPref(prefs::kMediaCacheSize);
 }