Web MIDI: enable midi_host.cc implementation on Android

content/browser/renderer_host/media/midi_host.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/media/midi_host.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/debug/trace_event.h"
 #include "base/process/process.h"
@@ skipping 92 matching lines @@
     return;
 
   // For now disallow all System Exclusive messages even if we
   // have permission.
   // TODO(toyoshim): allow System Exclusive if browser has granted
   // this client access.  We'll likely need to pass a GURL
   // here to compare against our permissions.
   if (data.size() > 0 && data[0] >= kSysExMessage)
       return;
 
-#if defined(OS_ANDROID)
-  // TODO(toyoshim): figure out why data() method does not compile on Android.

[scherkus (not reviewing), 2013/08/19 17:28:20]

AFAIK data() is part of C++11 :)

[Takashi Toyoshima, 2013/08/19 18:03:40]

Agreed. http://www.cplusplus.com/reference/vector/vector/

-  NOTIMPLEMENTED();
-#else
   midi_manager_->DispatchSendMIDIData(
       this,
       port,
-      data.data(),
+      &data.front(),

[scherkus (not reviewing), 2013/08/19 17:28:20]

FYI technically this would segfault calling front() if data was empty, but in my
local test program &data.front() returns a null pointer whereas data.front()
segfaults

stepping back a bit ... do you need to call this method if data is empty?
perhaps you can return earlier in the method?

[Takashi Toyoshima, 2013/08/19 18:03:40]

Oh, I didn't think empty cases.
Actually, a renderer execute send operation only if length > 0.
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...
But this runs in browser process. We should not trust renderers here.
I'll add size check.

       data.size(),
       timestamp);
-#endif
 
   sent_bytes_in_flight_ += data.size();
 }
 
 void MIDIHost::ReceiveMIDIData(
     int port_index,
     const uint8* data,
     size_t length,
     double timestamp) {
   TRACE_EVENT0("midi", "MIDIHost::ReceiveMIDIData");
@@ skipping 24 matching lines @@
 
   if (bytes_sent_since_last_acknowledgement_ >=
       kAcknowledgementThresholdBytes) {
     Send(new MIDIMsg_AcknowledgeSentData(
         bytes_sent_since_last_acknowledgement_));
     bytes_sent_since_last_acknowledgement_ = 0;
   }
 }
 
 }  // namespace content