[gcc 4.x] Fix the build failure due to -Werror=char-subscripts

Make the 'char' to 'unsigned char' to fix the following build failure.

device/hid/hid_connection_unittest.cc: In member function ‘virtual void device::HidConnectionTest_ReadWrite_Test::TestBody()’:
device/hid/hid_connection_unittest.cc:166:23: error: array subscript has type ‘char’ [-Werror=char-subscripts]
       buffer->data()[j] = i + j - 1;
                       ^
device/hid/hid_connection_unittest.cc:179:285: error: array subscript has type ‘char’ [-Werror=char-subscripts]
       ASSERT_EQ(i + j - 1, read_callback.buffer()->data()[j])

Review URL: https://codereview.chromium.org/664983002

Cr-Commit-Position: refs/heads/master@{#300238}

1 files changed, 2 insertions, 2 deletions

diff --git a/device/hid/hid_connection_unittest.cc b/device/hid/hid_connection_unittest.cc
index 5e48ef9..3607bf2 100644
--- a/device/hid/hid_connection_unittest.cc
+++ b/device/hid/hid_connection_unittest.cc
@@ -162,7 +162,7 @@ TEST_F(HidConnectionTest, ReadWrite) {
   for (char i = 0; i < 8; ++i) {
     scoped_refptr<IOBufferWithSize> buffer(new IOBufferWithSize(kBufferSize));
     buffer->data()[0] = 0;
-    for (char j = 1; j < kBufferSize; ++j) {
+    for (unsigned char j = 1; j < kBufferSize; ++j) {
       buffer->data()[j] = i + j - 1;
     }
 
@@ -175,7 +175,7 @@ TEST_F(HidConnectionTest, ReadWrite) {
     ASSERT_TRUE(read_callback.WaitForResult());
     ASSERT_EQ(9UL, read_callback.size());
     ASSERT_EQ(0, read_callback.buffer()->data()[0]);
-    for (char j = 1; j < kBufferSize; ++j) {
+    for (unsigned char j = 1; j < kBufferSize; ++j) {
       ASSERT_EQ(i + j - 1, read_callback.buffer()->data()[j]);
     }
   }