Fix a bug that H264BitReader::ReadBits cannot read more than 16 bits.

content/common/gpu/media/h264_bit_reader.cc

 // Copyright (c) 2012 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/common/gpu/media/h264_bit_reader.h"
 #include "base/logging.h"
 
 namespace content {
 
 H264BitReader::H264BitReader()
@@ skipping 48 matching lines @@
 // Read |num_bits| (1 to 31 inclusive) from the stream and return them
 // in |out|, with first bit in the stream as MSB in |out| at position
 // (|num_bits| - 1).
 bool H264BitReader::ReadBits(int num_bits, int *out) {
   int bits_left = num_bits;
   *out = 0;
   DCHECK(num_bits <= 31);
 
   while (num_remaining_bits_in_curr_byte_ < bits_left) {
     // Take all that's left in current byte, shift to make space for the rest.
-    *out = (curr_byte_ << (bits_left - num_remaining_bits_in_curr_byte_));
+    *out |= (curr_byte_ << (bits_left - num_remaining_bits_in_curr_byte_));
     bits_left -= num_remaining_bits_in_curr_byte_;
 
     if (!UpdateCurrByte())
       return false;
   }
 
   *out |= (curr_byte_ >> (num_remaining_bits_in_curr_byte_ - bits_left));
   *out &= ((1 << num_bits) - 1);
   num_remaining_bits_in_curr_byte_ -= bits_left;
 
@@ skipping 15 matching lines @@
     return true;
 
   // Last byte, look for stop bit;
   // We have more RBSP data if the last non-zero bit we find is not the
   // first available bit.
   return (curr_byte_ &
           ((1 << (num_remaining_bits_in_curr_byte_ - 1)) - 1)) != 0;
 }
 
 }  // namespace content