unittests: fix -Wnarrowing build errors

src/common/dwarf/dwarf2reader_die_unittest.cc

Index: src/common/dwarf/dwarf2reader_die_unittest.cc
diff --git a/src/common/dwarf/dwarf2reader_die_unittest.cc b/src/common/dwarf/dwarf2reader_die_unittest.cc
index 4e34436931924ba736453e2fcd353a279b2cb7f3..69f1f8ffd3859244a5e4fda98799da2b38698390 100644
--- a/src/common/dwarf/dwarf2reader_die_unittest.cc
+++ b/src/common/dwarf/dwarf2reader_die_unittest.cc
@@ -91,7 +91,7 @@ class MockDwarf2Handler: public Dwarf2Handler {
   MOCK_METHOD5(ProcessAttributeBuffer, void(uint64 offset,
                                             enum DwarfAttribute attr,
                                             enum DwarfForm form,
-                                            const char* data,
+                                            const uint8_t *data,
                                             uint64 len));
   MOCK_METHOD4(ProcessAttributeString, void(uint64 offset,
                                             enum DwarfAttribute attr,
@@ -132,9 +132,11 @@ struct DIEFixture {
     assert(info.GetContents(&info_contents));
     assert(abbrevs.GetContents(&abbrevs_contents));
     section_map.clear();
-    section_map[".debug_info"].first  = info_contents.data();
+    section_map[".debug_info"].first
+      = reinterpret_cast<const uint8_t *>(info_contents.data());
     section_map[".debug_info"].second = info_contents.size();
-    section_map[".debug_abbrev"].first  = abbrevs_contents.data();
+    section_map[".debug_abbrev"].first
+      = reinterpret_cast<const uint8_t *>(abbrevs_contents.data());
     section_map[".debug_abbrev"].second = abbrevs_contents.size();
     return section_map;
   }