Revert of Turn on pinch virtual-viewport by default on Windows (patchset #1...

Revert of Turn on pinch virtual-viewport by default on Windows (patchset #1 id:1 of https://codereview.chromium.org/516653002/)

Reason for revert:
Tentative revert to see if this is the cause of AppWindowInteractiveTest.TestInnerBounds failures on Win7 waterfall builders.

Original issue's description:
> Turn on pinch virtual-viewport by default on Windows
>
> BUG=148816
>
> Committed: https://chromium.googlesource.com/chromium/src/+/44fc05214f6c86da5c8f8d192f514ff55fb72932

TBR=cpu@chromium.org,luken@chromium.org,piman@chromium.org,bokan@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=148816

Review URL: https://codereview.chromium.org/549203002

Cr-Commit-Position: refs/heads/master@{#293754}

content/browser/gpu/compositor_util.cc

@@ -173,7 +173,7 @@ bool IsPinchVirtualViewportEnabled() {
   if (command_line.HasSwitch(cc::switches::kEnablePinchVirtualViewport))
     return true;
 
-#if defined(OS_CHROMEOS) || defined(OS_WIN)
+#if defined(OS_CHROMEOS)
   return true;
 #else
   return false;