Implement callback reactions for Custom Elements V1
This patch implements callbacks for Custom Elements V1:
1. Add Hooks to call methods in CustomElement class.
a. Element calls connected, disconnected, and attributeChanged.
b. CustomElementDefinition calls on upgrade.
2. CustomElement looks up CustomElementDefinition. Enqueueing reactions
were moved from CustomElement to CustomElementDefinition.
Implementing ScriptCustomElementDefinition to call JavaScript will be
in the following patch.
BUG=594918
Review-Url: https://codereview.chromium.org/2058823002
Cr-Commit-Position: refs/heads/master@{#399496}
19 files changed
