Hide the measuring stick

This patch fixes a bug where an empty line appeared below the about:tracing UI.
The empty line was caused by the measuring stick.

http://philbit.com/measuringstick.png shows the effect of this patch.
(left: fixed, right: broken)

BUG=
R=nduca@chromium.org

Review URL: https://codereview.appspot.com/9798048
Add mask and improve perspective on layer viewer

R=pdr@chromium.org

Review URL: https://codereview.appspot.com/9865043
Style fixes
Fix use of pendingPreAFs
Prevent caching on all resources

R=dsinclair@chromium.org

Review URL: https://codereview.appspot.com/9862043
Fix send_response implementation
Better error printing when raf explodes
Auto delete object instances at end of recording

Traces typically contain sequences of objects that are crated, snapshotted,
but never deleted, e.g.:
  id created 0x1000
  snapshot 0x1000
  snapshot 0x1000
  snapshot 0x1000

When this happens, we consider this object undeleted, and it has a deletionTs
of MAX_VALUE. This adds a pass after finalizing import that marks these with
a deletionTs of the maxValue of the model. This improves trace readability.
Move ObjectSnapshot to its own file
Allow tracks to be hidden by viewers

Some object views are registered, but not with the intention of giving them
a track in the UI. Now, when a view is registered, you can pass it an options
object, on which you can pass showInTrackView=false to prevent it from
appearing in the track view.

We use this to make the tile track not show up.
Better exception message when load_and_parse fails.
Remove stale css
Raise error when a non-tile is passed as a tile
Make LTHIV shrinkable. Should help when the LayerView is big.
Make raster highlight more opaque
Freshen the lthi_test_data file and make it synthetic so we can hack on it.
Add InfoBar
Normalize view registration scheme with object type registration scheme

ObjectSnapshotView and ObjectInstanceView used to have no unregister call
and thus the AnalysisView unit tests had to play games to test custom type
handling. This was silly.

This patch adds unreigster functions in the style of ObjectInstance and
ObjectSnapshot, and uses a custom try/finally block to register type handlers
and then tear them down.
Give default object views tag names.
Fix about_tracing.js