Inputs: Avoid implicit conversion of int to float with AxisNotify.

X and Y offsets calculated in OnAxisNotify are of type int.
AxisNotify has the function attributes as type float, thus
passed in attributes get converted to float type. These
values are used in BrowserProcessDispatcherDelegate and
passed to MouseWheelEvent constructor. MouseWheelEvent
function attributes are of type int. This CL fixes these
un-necessary implicit conversions by changing the function
attributes ( e.g. X and Y offset) of OnAxisNotify to type int.
Pointer: Fix type of state and flag attributes in ButtonNotfiy.

Currently, both types are defined as int. However, these should
be of ui::EventType and ui::EventFlags respectively. This CL fixes
the issue.
Input: Fix event type in KeyNotify.

Currently, it is of type unsigned when it should be of ui::EventType.
This CL fixes the issue.
Events: Introduce interface for event conversion.

Dispatcher is responsible for event conversion and also
for dispatching native events. We should move event conversion
out of dispatcher.This CL introduces the following classes:
1) EventConverterOzoneWayland: This class is same as
   WaylandDispatcherDelegate, with same responsibility.
2) EventConverterInProcess: This class is same as
   BrowserProcessDispatcherDelegate, with same responsibility
   and interface.
3) RemoteEventDispatcher: This class is same as
   GpuProcessDispatcherDelegate, with same responsibility and
   interface.

These classes will be taken into use in followup patches.
Use EventConverterOzoneWayland to convert native events to ui::Aura.

This CL takes into use EventConverterOzoneWayland. The changes are
pretty straightforward.
Dispatcher: Remove un-necessary apis from Dispatcher.

This patch removes all apis related to events and
WaylandDispatcherDelegate. EventConverterOzoneWayland is now
responsible for providing this functionality.
Dispatcher: Remove unnecessary classes.

This CL removes DispatcherDelegate and it's derived classes.