Do not cache the method name from PrettyMethod.

Restores parity with the cache that was present before the external API was
introduced.

Test: mmma art/
Test: mmma system/core/{libunwindstack,libbacktrace} and run host gtests
Bug: 119632407
Change-Id: If15114595513442b16fef47bb277bf43e781a658
diff --git a/libdexfile/external/dex_file_ext.cc b/libdexfile/external/dex_file_ext.cc
index 3c193f4..5c353b5 100644
--- a/libdexfile/external/dex_file_ext.cc
+++ b/libdexfile/external/dex_file_ext.cc
@@ -55,7 +55,6 @@
   int32_t offset;  // Offset relative to the start of the dex file header.
   int32_t len;
   int32_t index;  // Method index.
-  std::string name;  // Method name. Not filled in for all cache entries.
 };
 
 class MappedFileContainer : public DexFileContainer {
@@ -133,8 +132,7 @@
         int32_t offset = reinterpret_cast<const uint8_t*>(code.Insns()) - dex_file_->Begin();
         int32_t len = code.InsnsSizeInBytes();
         int32_t index = method.GetIndex();
-        auto res =
-            method_cache_.emplace(offset + len, art::MethodCacheEntry{offset, len, index, ""});
+        auto res = method_cache_.emplace(offset + len, art::MethodCacheEntry{offset, len, index});
         if (offset <= dex_offset && dex_offset < offset + len) {
           return &res.first->second;
         }
@@ -143,13 +141,6 @@
 
     return nullptr;
   }
-
-  const std::string& GetMethodName(art::MethodCacheEntry& entry) {
-    if (entry.name.empty()) {
-      entry.name = dex_file_->PrettyMethod(entry.index, false);
-    }
-    return entry.name;
-  }
 };
 
 int ExtDexFileOpenFromMemory(const void* addr,
@@ -312,7 +303,8 @@
   if (entry != nullptr) {
     method_info->offset = entry->offset;
     method_info->len = entry->len;
-    method_info->name = new ExtDexFileString{ext_dex_file->GetMethodName(*entry)};
+    method_info->name =
+        new ExtDexFileString{ext_dex_file->dex_file_->PrettyMethod(entry->index, false)};
     return true;
   }