Update the libmetrics API to match the new Chrome interface.

src/platform/metrics/metrics_library.cc

 // Copyright (c) 2010 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.
 
 /*
  * metrics_library.cc
  *
  *  Created on: Dec 1, 2009
  *      Author: sosa
  */
 
 #include "metrics_library.h"
 
 #include <errno.h>
 #include <sys/file.h>
 
 #include <cstdarg>
 #include <cstdio>
 #include <cstring>
 
 #define READ_WRITE_ALL_FILE_FLAGS \
   (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)
 
-static const char kAutotestPath[] = "/tmp/.chromeos-metrics-autotest";
-static const char kChromePath[] = "/tmp/.chromeos-metrics";
+static const char kAutotestPath[] =
+    "/var/log/metrics/autotest-events";
+static const char kChromePath[] =
+    "/var/log/metrics/uma-events";
 static const int32_t kBufferSize = 1024;
 
 using namespace std;
 
 // TODO(sosa@chromium.org) - use Chromium logger instead of stderr
 static void PrintError(const char *message, const char *file,
                        int code) {
   const char *kProgramName = "metrics_library";
   if (code == 0) {
     fprintf(stderr, "%s: %s\n", kProgramName, message);
   } else if (file == NULL) {
     fprintf(stderr, "%s: ", kProgramName);
     perror(message);
   } else {
     fprintf(stderr, "%s: %s: ", kProgramName, file);
     perror(message);
   }
 }
 
-// Sends message of size length to Chrome and returns true on success.
+// Sends message of size |length| to Chrome and returns true on success.
 static bool SendMessageToChrome(int32_t length, const char *message) {
   int chrome_fd = open(kChromePath,
                        O_WRONLY | O_APPEND | O_CREAT,
                        READ_WRITE_ALL_FILE_FLAGS);
   // If we failed to open it, return.
   if (chrome_fd < 0) {
     PrintError("open", kChromePath, errno);
     return false;
   }
 
@@ skipping 18 matching lines @@
 
   // Release the file lock and close file.
   if (flock(chrome_fd, LOCK_UN) < 0) {
     PrintError("unlock", kChromePath, errno);
     success = false;
   }
   close(chrome_fd);
   return success;
 }
 
-// Formats a name/value message for Chrome in buffer and returns the
+// Formats a name/value message for Chrome in |buffer| and returns the
 // length of the message or a negative value on error.
 //
 // Message format is: | LENGTH(binary) | NAME | \0 | VALUE | \0 |
 //
-// The arbitrary format argument covers the non-LENGTH portion of the
+// The arbitrary |format| argument covers the non-LENGTH portion of the
 // message. The caller is responsible to store the \0 character
 // between NAME and VALUE (e.g. "%s%c%d", name, '\0', value).
 static int32_t FormatChromeMessage(int32_t buffer_size, char *buffer,
                                    const char *format, ...) {
   int32_t message_length;
   size_t len_size = sizeof(message_length);
 
   // Format the non-LENGTH contents in the buffer by leaving space for
   // LENGTH at the start of the buffer.
   va_list args;
@@ skipping 12 matching lines @@
   if (message_length > buffer_size) {
     PrintError("chrome message too long", NULL, 0);
     return -1;
   }
 
   // Prepend LENGTH to the message.
   memcpy(buffer, &message_length, len_size);
   return message_length;
 }
 
-bool MetricsLibrary::SendToAutotest(string name, int value) {
+// static
+bool MetricsLibrary::SendToAutotest(const string& name, int value) {
   FILE *autotest_file = fopen(kAutotestPath, "a+");
   if (autotest_file == NULL) {
     PrintError("fopen", kAutotestPath, errno);
     return false;
   }
 
   fprintf(autotest_file, "%s=%d\n", name.c_str(), value);
   fclose(autotest_file);
   return true;
 }
 
-bool MetricsLibrary::SendToChrome(string name, int value) {
+// static
+bool MetricsLibrary::SendToChrome(const string& name, int sample,
+                                  int min, int max, int nbuckets) {
   // Format the message.
   char message[kBufferSize];
   int32_t message_length =
       FormatChromeMessage(kBufferSize, message,
-                          "%s%c%d", name.c_str(), '\0', value);
+                          "histogram%c%s %d %d %d %d", '\0',
+                          name.c_str(), sample, min, max, nbuckets);
 
   if (message_length < 0)
     return false;
 
   // Send the message.
   return SendMessageToChrome(message_length, message);
 }