db56a6f62c
Previously, the HighlightJS library (HLJS) was being Vulcanized into the PolyGerrit build, even if the library was not being used (for example if the user does not navigate to a diff or has syntax highlighting disabled in preferences). Because HLJS is a substantial file -- ranging in size from 47KB to more than 455KB (ungizpped) depending on the build environment, this is not ideal. In order to lazy load a JS library: 1) It needs to be copied into the built WAR file to be addressable, and 2) It should not be Vulcanized into the built gr-app.js file. Previously, the PolyGerrit build system supported copying and non-vulcanizing exactly one JS library: namely webcomponents-lite.js. This change generalizes the mechanism by which webcomponents is copied and adds HLJS to that list. This satisfies **1**. Furthermore, the GR-SYNTAX-LAYER is rewritten to dynamically import HLJS in the `process` step by crafting a SCRIPT element and attaching it to the local DOM. (Syntax processing is invoked only after entire diff is rendered.) Code that depends on the library awaits this load before using it. Thus, the conventional JS import can be removed from the element's HTML and will not be recognized by the Vulcanize phase. This satisfies **2**. Tests are updated accordingly. Bug: Issue 4298 Change-Id: I9a95d6d4c211cd8f1ca1bc4daec770b64b22b3d1