Change verify map writes capture option to verify buffer access.

* This option will now toggle on the behaviour to fill undefined buffer contents
  with a marker value, both if they're created without data (it will be zero
  filled instead) or mapped with discard (it will keep the old contents
  instead).
* There were too many hard to find problems or misconceptions about the buffer
  filling for it to be useful. Now it will be opt-in instead.

renderdoc/driver/d3d11/d3d11_device_wrap.cpp

@@ -45,8 +45,10 @@ bool WrappedID3D11Device::Serialise_CreateBuffer(SerialiserType &ser, const D3D1
   {
     fakeData.pSysMem = new byte[Descriptor.ByteWidth];
     fakeData.SysMemPitch = fakeData.SysMemSlicePitch = Descriptor.ByteWidth;
-    // fill with 0xfefefefe to indicate that the data is uninitialised.
-    memset((void *)fakeData.pSysMem, 0xfe, Descriptor.ByteWidth);
+    // fill with 0xdddddddd to indicate that the data is uninitialised, if that option is enabled
+    memset((void *)fakeData.pSysMem,
+           RenderDoc::Inst().GetCaptureOptions().verifyBufferAccess ? 0xdd : 0x0,
+           Descriptor.ByteWidth);
     pInitialData = &fakeData;
   }