src/vs/editor/common/model/tokenizationTextModelPart.ts/TokenizationTextModelPart/handleTokenizationProgress
class TokenizationTextModelPart:	private handleTokenizationProgress(completed: boolean) {
		if (this._backgroundTokenizationState === BackgroundTokenizationState.Completed) {
			// We already did a full tokenization and don't go back to progressing.
			return;
		}
		const newState = completed ? BackgroundTokenizationState.Completed : BackgroundTokenizationState.InProgress;
		if (this._backgroundTokenizationState !== newState) {
			this._backgroundTokenizationState = newState;
			this.bracketPairsTextModelPart.handleDidChangeBackgroundTokenizationState();
			this._onBackgroundTokenizationStateChanged.fire();
		}
	}