Terminal content goes missing when resizing (powershell/conpty)

[JasonDickens]

Issue Type: Bug

Using Powershell as terminal:
"terminal.integrated.shell.windows": "C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.exe",
"powershell.integratedConsole.showOnStartup": false,

1. Shrink terminal down to only displaying seven lines of text.
2. Change directory to a path that has many folders
3. Type dir
4. Scroll in the terminal and verify there is a long history.
5. Click Maximize Panel Size, or use keyboard shortcut to Toggle Maximized Panel
6. Observe you are no longer able to scroll up to view the console history.

Expected behavior: Console "top" is not reset and all output can be viewed
Actual behavior: Console history is lost.

This used to work correctly several versions ago and console history was preserved when the console was toggled. I use this by keeping my build watchers running in a small window at the bottom while I code and a hotkey to toggle the console maximize when I need to see the results of the watchers. Normally, I only need to see 3-4 lines when the watchers succeed, then when there's an error, I can toggle the maximize and scroll back to see the results. With this bug, my workflow is hindered greatly as I have to keep a separate console open and alt-tab over and over to see the results.

VS Code version: Code 1.36.1 (2213894, 2019-07-08T22:59:35.033Z)
OS version: Windows_NT x64 10.0.18362

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-7820X CPU @ 3.60GHz (16 x 3600)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_deferred_display_list: disabled_off skia_renderer: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	63.73GB (41.13GB free)
Process Argv	C:\g\PowerBIClients2\src
Screen Reader	no
VM	0%

Extensions (3)

Extension	Author (truncated)	Version
numbered-bookmarks	ale	6.2.1
gitlens	eam	9.9.3
pbi-vscode-tools	Mic	0.0.14

[Tyriar]

Looks like this is an issue with windows mode in xterm.js, we should not try to push the rows down when in windows mode like we do on *nix because conpty will redraw the screen and it always has overscroll. The edge case when the buffer is full might need to behave differently though.