[WebMIDI] Fix code style to suppress a static analysis error.

media/midi/usb_midi_output_stream.cc

 // Copyright 2014 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 "media/midi/usb_midi_output_stream.h"
 
 #include "base/logging.h"
 #include "media/midi/midi_message_util.h"
 #include "media/midi/usb_midi_device.h"
 
@@ skipping 103 matching lines @@
 }
 
 bool UsbMidiOutputStream::PushSysCommonMessage(
     const std::vector<uint8>& data,
     size_t* current,
     std::vector<uint8>* data_to_send) {
   size_t index = *current;
   uint8 first_byte = Get(data, index);
   DCHECK_LE(0xf1, first_byte);
   DCHECK_LE(first_byte, 0xf7);
+  DCHECK_EQ(0xf0, first_byte & 0xf8);
+  // There are only 6 message types (0xf1 - 0xf7), so the table size is 8.
   const size_t message_size_table[8] = {
     0, 2, 3, 2, 1, 1, 1, 0,
   };
-  size_t message_size = message_size_table[first_byte & 0x0f];
+  size_t message_size = message_size_table[first_byte & 0x07];
   DCHECK_NE(0u, message_size);
   DCHECK_LE(message_size, 3u);
 
   if (GetSize(data) < index + message_size) {
     // The message is incomplete.
     return false;
   }
 
   uint8 code_index = message_size == 1 ? 0x5 : static_cast<uint8>(message_size);
   data_to_send->push_back((jack_.cable_number << 4) | code_index);
@@ skipping 16 matching lines @@
   data_to_send->push_back(0);
   data_to_send->push_back(0);
   *current += 1;
 }
 
 bool UsbMidiOutputStream::PushChannelMessage(const std::vector<uint8>& data,
                                            size_t* current,
                                            std::vector<uint8>* data_to_send) {
   size_t index = *current;
   uint8 first_byte = Get(data, index);
+
   DCHECK_LE(0x80, (first_byte & 0xf0));
   DCHECK_LE((first_byte & 0xf0), 0xe0);
-
+  // There are only 7 message types (0x8-0xe in the higher four bits), so the
+  // table size is 8.
   const size_t message_size_table[8] = {
     3, 3, 3, 3, 2, 3, 3, 0,
   };
   uint8 code_index = first_byte >> 4;
+  DCHECK_LE(0x08, code_index);
+  DCHECK_LE(code_index, 0x0e);
   size_t message_size = message_size_table[code_index & 0x7];
   DCHECK_NE(0u, message_size);
   DCHECK_LE(message_size, 3u);
 
   if (GetSize(data) < index + message_size) {
     // The message is incomplete.
     return false;
   }
 
   data_to_send->push_back((jack_.cable_number << 4) | code_index);
   for (size_t i = index; i < index + 3; ++i)
     data_to_send->push_back(i < index + message_size ? Get(data, i) : 0);
   *current += message_size;
   return true;
 }
 
 }  // namespace media