COMPLETION_STATUS_KHR should be true on context loss

KHR_parallel_shader_compile COMPLETION_STATUS_KHR queries should return
true unconditionally when the context is lost. This is intended to
prevent applications from entering an infinite polling loop.

Spec clarification and test are landing upstream:
https://github.com/KhronosGroup/WebGL/pull/3188

Bug: angleproject:3379
Change-Id: I3c63235ccc3e07e0557e80021888886f893d268a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2559534
Auto-Submit: James Darpinian <jdarpinian@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831184}

third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc

@@ -3717,6 +3717,10 @@ ScriptValue WebGLRenderingContextBase::getProgramParameter(
     ScriptState* script_state,
     WebGLProgram* program,
     GLenum pname) {
+  // Completion status queries always return true on a lost context. This is
+  // intended to prevent applications from entering an infinite polling loop.
+  if (isContextLost() && pname == GL_COMPLETION_STATUS_KHR)
+    return WebGLAny(script_state, true);
   if (!ValidateWebGLProgramOrShader("getProgramParamter", program)) {
     return ScriptValue::CreateNull(script_state->GetIsolate());
   }
@@ -3829,6 +3833,10 @@ ScriptValue WebGLRenderingContextBase::getShaderParameter(
     ScriptState* script_state,
     WebGLShader* shader,
     GLenum pname) {
+  // Completion status queries always return true on a lost context. This is
+  // intended to prevent applications from entering an infinite polling loop.
+  if (isContextLost() && pname == GL_COMPLETION_STATUS_KHR)
+    return WebGLAny(script_state, true);
   if (!ValidateWebGLProgramOrShader("getShaderParameter", shader)) {
     return ScriptValue::CreateNull(script_state->GetIsolate());
   }