InputWindow: use read/writeStrongBinder

Still storing binder locally as a weak binder, but the plan is to remove
read/writeWeakBinder APIs. This is because weak binders can't be
promoted unless there is already a strong binder in a given process.

Bug: 137785053
Test: atest libgui_tests libinput_tests
Before and after:
libgui_test: Passed: 202, Failed: 1, Ignored: 0, Assumption Failed: 0
libinput_tests: Passed: 74, Failed: 0, Ignored: 0, Assumption Failed: 0

The ToT failure is:
[133/203] SurfaceTest#GetHdrSupport: FAILED (6ms)

Change-Id: I4e952672885a035174152286c529d82f55d48326
diff --git a/libs/input/InputWindow.cpp b/libs/input/InputWindow.cpp
index 5a60347..ec28757 100644
--- a/libs/input/InputWindow.cpp
+++ b/libs/input/InputWindow.cpp
@@ -99,7 +99,7 @@
     applicationInfo.write(output);
     output.write(touchableRegion);
     output.writeBool(replaceTouchableRegionWithCrop);
-    output.writeWeakBinder(touchableRegionCropHandle);
+    output.writeStrongBinder(touchableRegionCropHandle.promote());
     return OK;
 }
 
@@ -142,7 +142,7 @@
     ret.applicationInfo = InputApplicationInfo::read(from);
     from.read(ret.touchableRegion);
     ret.replaceTouchableRegionWithCrop = from.readBool();
-    ret.touchableRegionCropHandle = from.readWeakBinder();
+    ret.touchableRegionCropHandle = from.readStrongBinder();
 
     return ret;
 }