Revert 70618 - First pass at adding http/backend cache events to the NetLog. ...

Revert 70618 - First pass at adding http/backend cache events to the NetLog. 

Adds sources and events for ActiveCacheEntry and EntryImpl 
objects, as well as adding cache read/write events to 
HttpCacheTransactions. Most new read/write events are 
only logged when NetLog logging mode is set to log all events. 

Also, net-internals now merges begin and end events that have 
parameters, as long as only one of them has parameters. 
I think this increases readability, at the cost of making 
it a little more difficult to follow timings with just the "st" 
values. 

BUG=59382
TEST=none yet, other than updates to existing tests.

Review URL: http://codereview.chromium.org/4067002

TBR=mmenke@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=70619