unittests: fix -Wnarrowing build errors

src/common/dwarf/dwarf2diehandler_unittest.cc

Index: src/common/dwarf/dwarf2diehandler_unittest.cc
diff --git a/src/common/dwarf/dwarf2diehandler_unittest.cc b/src/common/dwarf/dwarf2diehandler_unittest.cc
index c0a532aa01624e15c9620b49239c01e9b4b85411..be91d2f45412237e57ef6e6a1e2ad7722e88f0c3 100644
--- a/src/common/dwarf/dwarf2diehandler_unittest.cc
+++ b/src/common/dwarf/dwarf2diehandler_unittest.cc
@@ -67,7 +67,7 @@ class MockDIEHandler: public DIEHandler {
   MOCK_METHOD3(ProcessAttributeReference,
                void(DwarfAttribute, DwarfForm, uint64));
   MOCK_METHOD4(ProcessAttributeBuffer,
-               void(DwarfAttribute, DwarfForm, const char *, uint64));
+               void(DwarfAttribute, DwarfForm, const uint8_t *, uint64));
   MOCK_METHOD3(ProcessAttributeString,
                void(DwarfAttribute, DwarfForm, const string &));
   MOCK_METHOD3(ProcessAttributeSignature,
@@ -86,7 +86,7 @@ class MockRootDIEHandler: public RootDIEHandler {
   MOCK_METHOD3(ProcessAttributeReference,
                void(DwarfAttribute, DwarfForm, uint64));
   MOCK_METHOD4(ProcessAttributeBuffer,
-               void(DwarfAttribute, DwarfForm, const char *, uint64));
+               void(DwarfAttribute, DwarfForm, const uint8_t *, uint64));
   MOCK_METHOD3(ProcessAttributeString,
                void(DwarfAttribute, DwarfForm, const string &));
   MOCK_METHOD3(ProcessAttributeSignature,
@@ -185,8 +185,9 @@ TEST(Dwarf2DIEHandler, PassAttributeValues) {
   MockRootDIEHandler mock_root_handler;
   DIEDispatcher die_dispatcher(&mock_root_handler);
 
-  const char buffer[10] = { 0x24, 0x24, 0x35, 0x9a, 0xca,
-                            0xcf, 0xa8, 0x84, 0xa7, 0x18 };
+  const uint8_t buffer[10] = {
+    0x24, 0x24, 0x35, 0x9a, 0xca, 0xcf, 0xa8, 0x84, 0xa7, 0x18
+  };
   string str = "\xc8\x26\x2e\x0d\xa4\x9c\x37\xd6\xfb\x1d";
 
   // Set expectations.