[Magnifier-86] Fix deadlock causing ANR

"main" prio=5 tid=1 Blocked
  | group="main" sCount=1 dsCount=0 flags=1 obj=0x74aeca00 self=0x7021814c00
  | sysTid=27953 nice=-10 cgrp=default sched=0/0 handle=0x70a85ff548
  | state=S schedstat=( 31382082536 9164116362 28130 ) utm=2661 stm=477 core=0 HZ=100
  | stack=0x7ff7a52000-0x7ff7a54000 stackSize=8MB
  | held mutexes=
  at android.widget.Magnifier$InternalPopupWindow.destroy(Magnifier.java:607)
  - waiting to lock <0x0ef5c351> (a java.lang.Object) held by thread 13
  at android.widget.Magnifier.dismiss(Magnifier.java:191)
  - locked <0x01cd07b6> (a java.lang.Object)

 "hwuiTask1" prio=5 tid=13 Blocked
  | group="main" sCount=1 dsCount=0 flags=1 obj=0x12f815d8 self=0x70000e7800
  | sysTid=28075 nice=-2 cgrp=default sched=0/0 handle=0x70046ba4f0
  | state=S schedstat=( 138800095 85604746 532 ) utm=10 stm=3 core=1 HZ=100
  | stack=0x70045bf000-0x70045c1000 stackSize=1009KB
  | held mutexes=
  at android.widget.Magnifier$InternalPopupWindow.lambda$doDraw$0(Magnifier.java:663)
  - waiting to lock <0x01cd07b6> (a java.lang.Object) held by thread 1
  - locked <0x0ef5c351> (a java.lang.Object)
  at android.widget.-$$Lambda$Magnifier$InternalPopupWindow$vZThyvjDQhg2J1GAeOWCNqy2iiw.onFrameDraw(lambda:-1)

Test: atest CtsWidgetTestCases:android.widget.cts.MagnifierTest
Change-Id: Idf0373ab0d5033d56da0f6f45d7d953f7e796813
Signed-off-by: Bin Chen <chenbin@vivo.com>