Terminal not response and take very high cpu

[eddylin]

Issue Type: Performance Issue

1. Open a terminal(cygwin)
2. ssh to a remote machine.
3. run a mysql query with a very large output.(about 260000 chars)
4. terminal is not responding and take very high cpu.

Happen in insider build and normal build.
This seem happen after 1.24.0

VS Code version: Code - Insiders 1.25.0-insider (7dc9539, 2018-06-15T05:17:41.405Z)
OS version: Windows_NT x64 10.0.16299

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-6400 CPU @ 2.70GHz (4 x 2712)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: enabled video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled
Memory (System)	15.88GB (6.19GB free)
Process Argv	C:\Program Files\Microsoft VS Code Insiders\Code - Insiders.exe
Screen Reader	no
VM	0%

Process Info

CPU %	Mem MB	   PID	Process
    0	    98	  5108	code-insiders main
    0	    64	  9284	   shared-process
    0	    76	 15424	   window (问题报告程序)
   25	   206	 20808	   window (Untitled-1 - Visual Studio Code - Insiders)
    0	    48	  2440	     extensionHost
    0	    13	 15056	     electron-crash-reporter
    0	    33	 21328	     terminal
    0	    10	 20688	       winpty-process
    0	    11	  2000	         console-window-host (Windows internal process)
    0	     4	  8500	         C:\Windows\system32\cmd.exe /c C:\cygwin64\Cygwin.bat
    0	    10	 19792	           bash  --login -i
    0	   122	 21596	   gpu-process

Workspace Info

;

Extensions: none

[Tyriar]

Tracked in xtermjs/xterm.js#1515