lshal: ListCommand::getPidInfo should be cached.

The function parses a big file and its result should be cached.
Add ListCommand::getPidInfoCached, which is a cached version
of this function.

Test: lshal_test
Change-Id: I03d8f149bf67b1512be431a3c4c29e83f7743a2f
diff --git a/cmds/lshal/ListCommand.h b/cmds/lshal/ListCommand.h
index 049533a..5af7ec2 100644
--- a/cmds/lshal/ListCommand.h
+++ b/cmds/lshal/ListCommand.h
@@ -85,7 +85,11 @@
     Status fetchBinderized(const sp<::android::hidl::manager::V1_0::IServiceManager> &manager);
     Status fetchAllLibraries(const sp<::android::hidl::manager::V1_0::IServiceManager> &manager);
 
+    // Get relevant information for a PID by parsing files under /d/binder.
+    // It is a virtual member function so that it can be mocked.
     virtual bool getPidInfo(pid_t serverPid, PidInfo *info) const;
+    // Retrieve from mCachedPidInfos and call getPidInfo if necessary.
+    const PidInfo* getPidInfoCached(pid_t serverPid);
 
     void dumpTable(const NullableOStream<std::ostream>& out) const;
     void dumpVintf(const NullableOStream<std::ostream>& out) const;
@@ -129,6 +133,9 @@
     // If an entry exist and not empty, it contains the cached content of /proc/{pid}/cmdline.
     std::map<pid_t, std::string> mCmdlines;
 
+    // Cache for getPidInfo.
+    std::map<pid_t, PidInfo> mCachedPidInfos;
+
     RegisteredOptions mOptions;
     // All selected columns
     std::vector<TableColumnType> mSelectedColumns;