Remove defunct Timer::alignedFireTime.

Tiny bit of cleanup: Some timers used to be 'snapped' to an 'aligned'
fire time so that work would get batched, particularly when suspended
timers were rescheduled. This sort of thing is now the responsibility of the
scheduler; nobody is using Timer::alignedFireTime any more.

Because alignedFireTime had no tests :O no tests were harmed in the
preparation of this changelist. :D

BUG=331912

Review URL: https://codereview.chromium.org/1625413002

Cr-Commit-Position: refs/heads/master@{#371775}

third_party/WebKit/Source/platform/Timer.h

@@ -86,8 +86,6 @@ private:
     NO_LAZY_SWEEP_SANITIZE_ADDRESS
     virtual bool canFire() const { return true; }
 
-    virtual double alignedFireTime(double fireTime) const { return fireTime; }
-
     void setNextFireTime(double now, double delay);
 
     void runInternal();