Fix to remove /wd4018 (-Wno-sign-compare) for /device/bluetooth

This is a part of effort to remove /wd4018 warning suppression.

Master CL is
https://chromium-review.googlesource.com/c/chromium/src/+/1152755

This CL was uploaded by git cl split.

R=ortuno@chromium.org

Bug: 868248, 588506
Change-Id: I6f381e608322431356681f57a315271dca409d83
Reviewed-on: https://chromium-review.googlesource.com/1152843Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578899}

device/bluetooth/bluetooth_uuid_unittest.cc

@@ -106,7 +106,7 @@ TEST(BluetoothUUIDTest, GetCanonicalValueAsGUID) {
   const char kValid128Bit0[] = "12345678-1234-5678-9abc-def123456789";
   GUID guid = BluetoothUUID::GetCanonicalValueAsGUID(kValid128Bit0);
 
-  EXPECT_EQ(0x12345678, guid.Data1);
+  EXPECT_EQ(0x12345678u, guid.Data1);
   EXPECT_EQ(0x1234, guid.Data2);
   EXPECT_EQ(0x5678, guid.Data3);
   EXPECT_EQ(0x9a, guid.Data4[0]);