Reviewers: ihab.awad,
Description:
Defer the construction of taming ctors and their prototypes until an
instance is going to be created, or the inert ctor global (e.g.
window.Element) is accessed.
This reduces the startup time of Domado, and eliminates nearly all of
the time cost of supporting features which are not used by the guest
content (e.g. XMLHttpRequest or <canvas>).
This is also part of the refactoring-Domado project: the lazy loading
enforces a lack of imperative dependencies between individual taming
classes.
Certain fundamental classes are not made lazy, as they would always
be loaded and disentangling them would be additional work, such as
Node, Element, Window, and Document. I expect to move these to the
same lazy infrastructure as part of future refactoring.
Supporting changes:
* Events created by document.createEvent() are no longer a distinct
type; the notYetDispatched flag turns out to be exactly sufficient
(and secure) for the distinctions we need to make.
* Newly visible-to-the-guest types:
CSSStyleDeclaration (old laziness kludge didn't allow exporting)
ImageData (now uses prototype inheritance)
CajaComputedCSSStyleDeclaration (implementation detail)
CajaFormField (implementation detail)
* Added a REPL which evaluates inside the sandbox, for debugging
(linked from test-index.html).
* TameImageData now uses prototype inheritance.
* Fixed scanner's check for taming ctors leaking having been broken
by the move to a single SES frame.
* Scanner is aware of newly exported CSSStyleDeclaration
Performance notes:
Measuring using console.time() in Chrome, approximately 130 ms is
removed from the run time of attachDocument; this figure is adjusted
for the cost of lazy loading that always happens, namely Event for
onload events.
Test run time changes (Firefox; one run, so very noisy). domado-global
particularly benefits because all it does is start many trivial guests.
guest-domado-global-es53-min 15.956/26.862 = 0.59
guest-domado-global-es5-min 3.519 /4.684 = 0.75
cajajs-invocation-nomin-es53 28.556/24.015 = 1.18
cajajs-invocation-nomin-es5 6.252 /6.298 = 0.99
cajajs-invocation-min-es53 24.473/22.089 = 1.10
cajajs-invocation-min-es5 6.656 /5.245 = 1.26
guest-domado-dom-es53-min 12.551/13.500 = 0.92
guest-domado-dom-es5-min 5.339 /5.117 = 1.04
Please review this at https://codereview.appspot.com/10240043/
Affected files:
M src/com/google/caja/plugin/domado.js
M tests/com/google/caja/plugin/es53-test-scan-guest.js
A tests/com/google/caja/plugin/repl.html
M tests/com/google/caja/plugin/test-index.html
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