Regression: unnecessary assignment using SIMPLE_OPTIMIZATIONS

I have updated to the latest version v20180610 from the one I was using (v20170806) and I found the code below to add an unnecessary assignment on class constructors:

/**
 * @constructor
 * @struct
 * @param {number} x
 * @param {number} y
 */
function Character( x, y ) {
    this.m_x = x;
    this.m_y = y;
};
/**
 * @constructor
 * @struct
 * @param {number} x
 * @param {number} y
 */
function FroggerPlayer( x, y ) {
    this.m_character = null;
    this.m_character = new Character( x, y );
};

Previously this code was minified to:

function Character(a, b) {
	this.m_x = a;
	this.m_y = b
}
function FroggerPlayer(a, b) {
	this.m_character = new Character(a, b)
};

But now is minified to:

function Character(a, b) {
	this.m_x = a;
	this.m_y = b
}
function FroggerPlayer(a, b) {
	this.m_character = null;
	this.m_character = new Character(a, b)
};

The compilation flags are: --language_in ECMASCRIPT5_STRICT --compilation_level SIMPLE_OPTIMIZATIONS

[lauraharker]

Assigning to myself to investigate because I suspect this is because of https://github.com/google/closure-compiler/commit/627f90f54952f0601bef6d5057675fd196d46a6b#diff-a55a956858d023be41b94bae129c5794

[ex]

Closing this.