ESSL3 introduces implicit array size that is determined automatically
according to the initializer. Implicit sizes are resolved when parsing
constructors and when initializers are evaluated, so ANGLE's AST will not
contain implicit sizes.

Declarations where there are two differently sized arrays with the same
implicitly sized type, for example:

float[] a = float[](0.0), b = float[](0.0, 1.0);

will be transformed into declarations where the two arrays don't share
the array size like this:

float a[1] = float[1](0.0), float b[2] = float[2](0.0, 1.0);

so they are not a problem.

Unlike sized arrays, implicitly sized arrays don't have a size limit
enforced by the parser.

Include a test that verifies that non-initialization of an implicitly
sized array defined using ESSL3 type syntax is caught by the parser.

Additionally tested with WebGL 2 test
sdk/tests/deqp/data/gles3/shaders/arrays.html

TEST=WebGL 2 conformance tests, angle_unittests
BUG=angleproject:941

Change-Id: Ib55b7601848102a103af9db284a80f09abaeb021
Reviewed-on: https://chromium-review.googlesource.com/265653Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>