unittests: fix -Wnarrowing build errors

src/common/dwarf_cu_to_module.cc

Index: src/common/dwarf_cu_to_module.cc
diff --git a/src/common/dwarf_cu_to_module.cc b/src/common/dwarf_cu_to_module.cc
index 1729d4ac93af0ac80048fcc7b10a22e41aa16b47..a4f061c0ec959119d1c34c00cbf83a6e3e9712c5 100644
--- a/src/common/dwarf_cu_to_module.cc
+++ b/src/common/dwarf_cu_to_module.cc
@@ -140,7 +140,7 @@ DwarfCUToModule::FileContext::~FileContext() {
 }
 
 void DwarfCUToModule::FileContext::AddSectionToSectionMap(
-    const string& name, const char* contents, uint64 length) {
+    const string& name, const uint8_t *contents, uint64 length) {
   section_map_[name] = std::make_pair(contents, length);
 }
 
@@ -814,7 +814,7 @@ void DwarfCUToModule::ReadSourceLines(uint64 offset) {
     cu_context_->reporter->MissingSection(".debug_line");
     return;
   }
-  const char *section_start = map_entry->second.first;
+  const uint8_t *section_start = map_entry->second.first;
   uint64 section_length = map_entry->second.second;
   if (offset >= section_length) {
     cu_context_->reporter->BadLineInfoOffset(offset);