Increase test coverage of haeley-webgl

[bakoe]

As long as coveralls is not set-up for the repository, here is a current coverage report created by running npm run test:nyc on commit c8a002d:

-----------------------|---------|----------|---------|---------|-------------------
File                   | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-----------------------|---------|----------|---------|---------|-------------------
All files              |    20.2 |    10.81 |    19.3 |    19.6 |
 about.ts              |     100 |      100 |     100 |     100 |
 allocationregister.ts |     100 |      100 |     100 |     100 |
 buffer.ts             |       0 |        0 |       0 |       0 | 4-188
 changelookup.ts       |     100 |      100 |     100 |     100 |
 context.ts            |    6.32 |     2.85 |    2.08 |    6.32 | 88-1194
 contextmasquerade.ts  |      86 |       75 |   88.88 |      86 | 116-124
 extensions.ts         |     100 |      100 |     100 |     100 |
 extensionshash.ts     |     100 |      100 |     100 |     100 |
 formatbytesizes.ts    |    7.89 |        0 |       0 |    7.89 | 20-146,159-181
 framebuffer.ts        |       0 |        0 |       0 |       0 | 4-506
 geometry.ts           |       0 |        0 |       0 |       0 | 6-129
 gl2facade.ts          |    2.47 |        0 |       0 |    2.52 | 27-464
 initializable.ts      |   82.25 |      100 |   82.75 |   82.69 | 127-142
 object.ts             |   83.33 |      100 |   66.66 |   83.33 | 105,138-147
 program.ts            |       0 |        0 |       0 |       0 | 4-240
 renderbuffer.ts       |       0 |        0 |       0 |       0 | 4-203
 shader.ts             |       0 |        0 |       0 |       0 | 4-198
 texture2d.ts          |       0 |        0 |       0 |       0 | 4-451
 vertexarray.ts        |       0 |        0 |       0 |       0 | 4-136
 wizard.ts             |       0 |        0 |       0 |       0 | 4-107
-----------------------|---------|----------|---------|---------|-------------------

Colored: