AU: Many minor cleanup changes

src/platform/update_engine/download_action.cc

 // Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/download_action.h"
 #include <errno.h>
 #include <algorithm>
+#include <string>
+#include <vector>
 #include <glib.h>
 #include "update_engine/action_pipe.h"
+#include "update_engine/subprocess.h"
 
 using std::min;
+using std::string;
+using std::vector;
 
 namespace chromeos_update_engine {
 
 DownloadAction::DownloadAction(HttpFetcher* http_fetcher)
     : writer_(NULL),
       http_fetcher_(http_fetcher) {}
 
 DownloadAction::~DownloadAction() {}
 
 void DownloadAction::PerformAction() {
@@ skipping 55 matching lines @@
 }
 
 void DownloadAction::ReceivedBytes(HttpFetcher *fetcher,
                                    const char* bytes,
                                    int length) {
   int rc = writer_->Write(bytes, length);
   TEST_AND_RETURN(rc >= 0);
   omaha_hash_calculator_.Update(bytes, length);
 }
 
+namespace {
+void FlushLinuxCaches() {
+  vector<string> command;
+  command.push_back("/bin/sync");
+  int rc;
+  LOG(INFO) << "FlushLinuxCaches/sync...";
+  Subprocess::SynchronousExec(command, &rc);
+  LOG(INFO) << "FlushLinuxCaches/drop_caches...";
+
+  const char* const drop_cmd = "3\n";
+  utils::WriteFile("/proc/sys/vm/drop_caches", drop_cmd, strlen(drop_cmd));
+
+  LOG(INFO) << "FlushLinuxCaches done.";
+}
+}
+
 void DownloadAction::TransferComplete(HttpFetcher *fetcher, bool successful) {
   if (writer_) {
     CHECK_EQ(writer_->Close(), 0) << errno;
     writer_ = NULL;
   }
   if (successful) {
     // Make sure hash is correct
     omaha_hash_calculator_.Finalize();
     if (omaha_hash_calculator_.hash() != install_plan_.download_hash) {
       LOG(ERROR) << "Download of " << install_plan_.download_url
                  << " failed. Expect hash " << install_plan_.download_hash
                  << " but got hash " << omaha_hash_calculator_.hash();
       successful = false;
     }
   }
+  
+  FlushLinuxCaches();
 
   // Write the path to the output pipe if we're successful
   if (successful && HasOutputPipe())
     SetOutputObject(GetInputObject());
   processor_->ActionComplete(this, successful);
 }
 
 };  // namespace {}