adb_profile_chrome: Check in perf-to-tracing conversion script

Check in perf-to-tracing conversion script. This lets the --perf command
line switch actually produce trace files that can be loaded by Trace
Viewer.

The conversion script was originally written by Victor Miura
<vmiura@chromium.org> in https://codereview.chromium.org/296623002/.

TEST=PerfControllerTest
BUG=375754

Review URL: https://codereview.chromium.org/404543003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285022 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 605 insertions, 11 deletions

diff --git a/tools/profile_chrome/perf_controller.py b/tools/profile_chrome/perf_controller.py
index 245435e..c2cef2c 100644
--- a/tools/profile_chrome/perf_controller.py
+++ b/tools/profile_chrome/perf_controller.py
@@ -4,6 +4,7 @@
 
 import logging
 import os
+import signal
 import subprocess
 import sys
 import tempfile
@@ -170,9 +171,8 @@ class PerfProfilerController(controllers.BaseController):
         perf_profile, symfs_dir, required_libs, kallsyms))
 
     # Convert the perf profile into JSON.
-    perf_script_path = os.path.join(constants.DIR_SOURCE_ROOT,
-        'tools', 'telemetry', 'telemetry', 'core', 'platform', 'profiler',
-        'perf_vis', 'perf_to_tracing.py')
+    perf_script_path = os.path.join(os.path.dirname(os.path.abspath(__file__)),
+                                    'third_party', 'perf_to_tracing.py')
     json_file_name = os.path.basename(perf_profile)
     with open(os.devnull, 'w') as dev_null, \
         open(json_file_name, 'w') as json_file:
diff --git a/tools/profile_chrome/perf_controller_unittest.py b/tools/profile_chrome/perf_controller_unittest.py
index fbc226f..44bfbfa 100644
--- a/tools/profile_chrome/perf_controller_unittest.py
+++ b/tools/profile_chrome/perf_controller_unittest.py
@@ -35,14 +35,6 @@ class PerfProfilerControllerTest(controllers_unittest.BaseControllerTest):
       controller.StopTracing()
 
     result = controller.PullTrace()
-    # Perf-to-JSON conversion can fail if dependencies are missing.
-    if not result:
-      perf_script_path = os.path.join(constants.DIR_SOURCE_ROOT,
-          'tools', 'telemetry', 'telemetry', 'core', 'platform', 'profiler',
-          'perf_vis', 'perf_to_tracing.py')
-      assert not os.path.exists(perf_script_path)
-      return
-
     try:
       with open(result) as f:
         json.loads(f.read())
diff --git a/tools/profile_chrome/third_party/COPYING b/tools/profile_chrome/third_party/COPYING
new file mode 100644
index 0000000..d159169d
--- /dev/null
+++ b/tools/profile_chrome/third_party/COPYING
@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
+    machine-readable copy of the corresponding source code, to be
+    distributed under the terms of Sections 1 and 2 above on a medium
+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable.  However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices.  Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+                            NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/tools/profile_chrome/third_party/README.chromium b/tools/profile_chrome/third_party/README.chromium
new file mode 100644
index 0000000..5f58a65
--- /dev/null
+++ b/tools/profile_chrome/third_party/README.chromium
@@ -0,0 +1,15 @@
+Name: Perf to JSON conversion script
+Short Name: perf_to_json
+URL: http://www.chromium.org
+Version: 0
+Date: 21.7.2014
+Revision: 0
+License: GPL
+License File: NOT_SHIPPED
+Security Critical: No
+
+Description:
+Script for converting perf script events into tracing JSON.
+
+Local Modifications:
+None.
diff --git a/tools/profile_chrome/third_party/perf_to_tracing.py b/tools/profile_chrome/third_party/perf_to_tracing.py
new file mode 100644
index 0000000..280937a
--- /dev/null
+++ b/tools/profile_chrome/third_party/perf_to_tracing.py
@@ -0,0 +1,248 @@
+# Script for converting perf script events into tracing JSON.
+#
+# Generated by perf script -g python
+# Licensed under the terms of the GNU GPL License version 2
+
+import json
+import os
+import sys
+
+from collections import deque
+
+
+# Categorize DSOs by component.
+dso_to_comp = {
+    'libdvm.so': 'Java',
+    'libart.so': 'Java',
+    'libjavacore.so': 'Java',
+    'libandroid_runtime.so': 'Android',
+    'libgui.so': 'Android',
+    'libui.so': 'Android',
+    'libbinder.so': 'Android',
+    'libmemalloc.so': 'Android',
+    'libcrypto.so': 'Android',
+    'libcutils.so':'Android',
+    'libutils.so': 'Android',
+    '[kernel.kallsyms]': 'Kernel',
+    'libc.so': 'Standard Lib',
+    'libstdc++.so': 'Standard Lib',
+    'libm.so':'Standard Lib',
+    'libGLESv2_adreno.so': 'GPU Driver',
+    'libGLESv2_adreno200.so': 'GPU Driver',
+    'libq3dtools_adreno200.so': 'GPU Driver',
+    'libEGL_adreno.so': 'GPU Driver',
+    'libEGL_adreno200.so': 'GPU Driver',
+    'libEGL.so': 'GPU Driver',
+    'libgsl.so': 'GPU Driver',
+    'libGLESv2.so': 'GPU Driver',
+    'libsc-a3xx.so': 'GPU Driver',
+    'libadreno_utils.so': 'GPU Driver',
+    'eglsubAndroid.so': 'GPU Driver',
+    'gralloc.msm8960.so': 'GPU Driver',
+    'libadreno_utils': 'GPU Driver',
+    'libGLES_mali.so': 'GPU Driver',
+    'libchromeview.so': 'Chrome',
+    '[unknown]': '<unknown>',
+    '[UNKNOWN]': '<unknown>',
+}
+
+
+def FilterSymbolModule(module):
+  m = dso_to_comp.get(module, None)
+  if m:
+    return m
+  if module.find('libchrome.') == 0:
+    return 'Chrome'
+  if module.find('dalvik') >= 0 or module.find('@') >= 0:
+    return 'Java'
+  return module
+
+
+def FilterSymbolName(module, orign_module, name):
+  if module == 'Java':
+    return name
+  elif module == 'GPU Driver':
+    return name
+  if name == '':
+    return orign_module + ':unknown'
+  if name[0].isdigit() or name == '(nil)':
+    return orign_module + ':unknown'
+  return name
+
+
+class StackFrameNode:
+  def __init__(self, stack_id, name, category):
+    self.stack_id = stack_id
+    self.parent_id = 0
+    self.children = {}
+    self.category = category
+    self.name = name
+    self.samples = []
+    self.total_weight = 0.0
+    self.have_total_weight = False
+    self.parent = None
+
+  def ToDict(self, out_dict):
+    if self.stack_id:
+      node_dict = {}
+      node_dict['name'] = self.name
+      node_dict['category'] = self.category
+      if self.parent_id:
+        node_dict['parent'] = self.parent_id
+
+      out_dict[self.stack_id] = node_dict
+
+    for child in self.children.values():
+      child.ToDict(out_dict)
+    return out_dict
+
+  def GetTotalWeight(self):
+    if self.have_total_weight:
+      return self.total_weight
+    else:
+      # Sum up self samples weight, and children's total weights.
+      for s in self.samples:
+        self.total_weight += s.weight
+      for c in self.children.values():
+        self.total_weight += c.GetTotalWeight()
+      self.have_total_weight = True
+      return self.total_weight
+
+
+class PerfSample:
+  def __init__(self, stack_id, ts, cpu, tid, weight, samp_type, comm):
+    self.stack_id = stack_id
+    self.ts = ts
+    self.cpu = cpu
+    self.tid = tid
+    self.weight = weight
+    self.type = samp_type
+    self.comm = comm
+
+  def ToDict(self):
+    ret = {}
+    ret['ts'] = self.ts / 1000.0  # Timestamp in microseconds
+    ret['tid'] = self.tid  # Thread id
+    ret['cpu'] = self.cpu  # Sampled CPU
+    ret['weight'] = self.weight  # Sample weight
+    ret['name'] = self.type  # Sample type
+    ret['comm'] = self.comm  # Sample type
+    assert self.stack_id != 0
+    if self.stack_id:
+      ret['sf'] = self.stack_id  # Stack frame id
+    return ret
+
+
+samples = []
+root_chain = StackFrameNode(0, 'root', '[unknown]')
+next_stack_id = 1
+tot_period = 0
+saved_period = 0
+
+
+def process_event(param_dict):
+  global next_stack_id
+  global saved_period
+  global tot_period
+
+  samp_comm = param_dict['comm']
+  samp_tid = param_dict['tid']
+  samp_cpu = param_dict['cpu']
+  samp_ts = param_dict['time']
+  samp_period = param_dict['period']
+  samp_type = param_dict['ev_name']
+  tot_period += samp_period
+
+  # Parse call chain.
+  seen_syms = set()
+  chain = deque()
+  for cs in param_dict['cs']:
+    cs_name = cs[0]
+    cs_dso = os.path.basename(cs[1])
+    cs_category = FilterSymbolModule(cs_dso)
+    cs_name = FilterSymbolName(cs_category, cs_dso, cs_name)
+
+    if cs_category != '<unknown>' or len(chain) == 0:
+      sym = (cs_name, cs_category)
+      if sym in seen_syms:
+        while chain[0] != sym:
+          seen_syms.remove(chain[0])
+          chain.popleft()
+      else:
+        seen_syms.add(sym)
+        chain.appendleft(sym)
+
+      # Discard garbage stacktrace before __pthread_start()
+      if cs_name == '__pthread_start(void*)':
+        break
+
+  # Done reading call chain.  Add to stack frame tree.
+  stack_frame = root_chain
+  for call in chain:
+    if call in stack_frame.children:
+      stack_frame = stack_frame.children[call]
+    else:
+      new_node = StackFrameNode(next_stack_id, call[0], call[1])
+      next_stack_id += 1
+      new_node.parent_id = stack_frame.stack_id
+      stack_frame.children[call] = new_node
+      stack_frame = new_node
+
+  # Save sample.
+  sample = PerfSample(stack_frame.stack_id,
+                  samp_ts,
+                  samp_cpu,
+                  samp_tid,
+                  samp_period,
+                  samp_type,
+                  samp_comm)
+  samples.append(sample)
+  stack_frame.samples.append(sample)
+  saved_period += samp_period
+
+
+def trace_begin():
+  pass
+
+
+def trace_end():
+  # Return siblings of a call tree node.
+  def GetNodeSiblings(node):
+    if not node:
+      return []
+    if not node.parent:
+      return []
+    return node.parent.children.values()
+
+  # Try to reduce misplaced stack leaves by moving them up into sibling nodes.
+  def FixCallTree(node, parent):
+    # Get siblings of node's parent.
+    node.parent = parent
+    parent_siblings = GetNodeSiblings(parent)
+
+    # If parent's sibling has same node name, has no children and small weight,
+    # transplant sibling's samples into the current node.
+    for sibling in parent_siblings:
+      if sibling.name == node.name and \
+          len(sibling.children) == 0 and \
+          sibling.GetTotalWeight() <= node.GetTotalWeight() * 0.15:
+
+        # Transplant samples from sibling to current node.
+        for samp in sibling.samples:
+          samp.stack_id = node.stack_id
+          node.samples.append(samp)
+        sibling.samples = []
+        break
+
+    # Recurse child nodes.
+    for c in node.children.values():
+      FixCallTree(c, node)
+
+  FixCallTree(root_chain, None)
+
+  trace_dict = {}
+  trace_dict['samples'] = [s.ToDict() for s in samples]
+  trace_dict['stackFrames'] = root_chain.ToDict({})
+  trace_dict['traceEvents'] = []
+
+  json.dump(trace_dict, sys.stdout, indent=1)