Fix preparing log file name.

Problem:
Excuting with flags as "--prof --logfile-per-isolate --logfile=/path/to/filename"
expected file name: /path/to/isolate-<isolate id>-filename
current result: isolate-<isolate id>-/path/to/filename

This patch makes the file name we expected.

Review URL: https://codereview.chromium.org/960813004

Cr-Commit-Position: refs/heads/master@{#26955}

AUTHORS

@@ -63,6 +63,7 @@ James Pike <g00gle@chilon.net>
 Jianghua Yang <jianghua.yjh@alibaba-inc.com>
 Joel Stanley <joel@jms.id.au>
 Jonathan Liu <net147@gmail.com>
+JunHo Seo <sejunho@gmail.com>
 Kang-Hao (Kenny) Lu <kennyluck@csail.mit.edu>
 Luis Reis <luis.m.reis@gmail.com>
 Luke Zarko <lukezarko@gmail.com>

src/base/platform/platform-posix.cc

@@ -356,6 +356,11 @@ bool OS::Remove(const char* path) {
 }
 
 
+bool OS::isDirectorySeparator(const char ch) {
+  return ch == '/';
+}
+
+
 FILE* OS::OpenTemporaryFile() {
   return tmpfile();
 }

src/base/platform/platform-win32.cc

@@ -575,6 +575,11 @@ bool OS::Remove(const char* path) {
 }
 
 
+bool OS::isDirectorySeparator(const char ch) {
+  return ch == '/' || ch == '\\';
+}
+
+
 FILE* OS::OpenTemporaryFile() {
   // tmpfile_s tries to use the root dir, don't use it.
   char tempPathBuffer[MAX_PATH];

src/base/platform/platform.h

@@ -142,6 +142,8 @@ class OS {
   static FILE* FOpen(const char* path, const char* mode);
   static bool Remove(const char* path);
 
+  static bool isDirectorySeparator(const char ch);
+
   // Opens a temporary file, the file is auto removed on close.
   static FILE* OpenTemporaryFile();
 

src/log.cc

@@ -1767,8 +1767,16 @@ static void AddIsolateIdIfNeeded(std::ostream& os,  // NOLINT
 
 static void PrepareLogFileName(std::ostream& os,  // NOLINT
                                Isolate* isolate, const char* file_name) {
-  AddIsolateIdIfNeeded(os, isolate);
+  int dir_separator_count = 0;
   for (const char* p = file_name; *p; p++) {
+    if (base::OS::isDirectorySeparator(*p)) dir_separator_count++;
+  }
+
+  for (const char* p = file_name; *p; p++) {
+    if (dir_separator_count == 0) {
+      AddIsolateIdIfNeeded(os, isolate);
+      dir_separator_count--;
+    }
     if (*p == '%') {
       p++;
       switch (*p) {
@@ -1794,6 +1802,7 @@ static void PrepareLogFileName(std::ostream& os,  // NOLINT
           break;
       }
     } else {
+      if (base::OS::isDirectorySeparator(*p)) dir_separator_count--;
       os << *p;
     }
   }