Update dexpreopt_test to verify boot images.

This ensures that odrefresh does not unexpectedly override the boot
image on /system on the first boot.

Bug: 203492478
Test: Build a system image, flash it to a device, and run
  `atest art_standalone_dexpreopt_test`.
Change-Id: Id02e60612e6b3c12876cc8707e6d2be3866a5b6f
diff --git a/libartbase/base/common_art_test.cc b/libartbase/base/common_art_test.cc
index 20bc87c..593ea25 100644
--- a/libartbase/base/common_art_test.cc
+++ b/libartbase/base/common_art_test.cc
@@ -50,7 +50,6 @@
 #include "dex/primitive.h"
 #include "gtest/gtest.h"
 #include "nativehelper/scoped_local_ref.h"
-#include "procinfo/process.h"
 
 namespace art {
 
@@ -680,12 +679,16 @@
 std::vector<pid_t> GetPidByName(const std::string& process_name) {
   std::vector<pid_t> results;
   for (pid_t pid : android::base::AllPids{}) {
-    android::procinfo::ProcessInfo process_info;
-    std::string error;
-    if (!android::procinfo::GetProcessInfo(pid, &process_info, &error)) {
+    std::string cmdline;
+    if (!android::base::ReadFileToString(StringPrintf("/proc/%d/cmdline", pid), &cmdline)) {
       continue;
     }
-    if (process_info.name == process_name) {
+    // Take the first argument.
+    size_t pos = cmdline.find('\0');
+    if (pos != std::string::npos) {
+      cmdline.resize(pos);
+    }
+    if (cmdline == process_name) {
       results.push_back(pid);
     }
   }