unittests: fix -Wnarrowing build errors

src/common/dwarf/bytereader.cc

Index: src/common/dwarf/bytereader.cc
diff --git a/src/common/dwarf/bytereader.cc b/src/common/dwarf/bytereader.cc
index 6802026449bd52af6477ff8d9acc1293cde831c6..d3045149722bd4987dd0c993f0bc773fba45834f 100644
--- a/src/common/dwarf/bytereader.cc
+++ b/src/common/dwarf/bytereader.cc
@@ -62,7 +62,7 @@ void ByteReader::SetAddressSize(uint8 size) {
   }
 }
 
-uint64 ByteReader::ReadInitialLength(const char* start, size_t* len) {
+uint64 ByteReader::ReadInitialLength(const uint8_t *start, size_t* len) {
   const uint64 initial_length = ReadFourBytes(start);
   start += 4;
 
@@ -100,7 +100,7 @@ bool ByteReader::UsableEncoding(DwarfPointerEncoding encoding) const {
   }
 }
 
-uint64 ByteReader::ReadEncodedPointer(const char *buffer,
+uint64 ByteReader::ReadEncodedPointer(const uint8_t *buffer,
                                       DwarfPointerEncoding encoding,
                                       size_t *len) const {
   // UsableEncoding doesn't approve of DW_EH_PE_omit, so we shouldn't
@@ -129,7 +129,7 @@ uint64 ByteReader::ReadEncodedPointer(const char *buffer,
     // Round up to the next boundary.
     uint64 aligned = (offset + AddressSize() - 1) & -AddressSize();
     // Convert back to a pointer.
-    const char *aligned_buffer = buffer_base_ + (aligned - skew);
+    const uint8_t *aligned_buffer = buffer_base_ + (aligned - skew);
     // Finally, store the length and actually fetch the pointer.
     *len = aligned_buffer - buffer + AddressSize();
     return ReadAddress(aligned_buffer);