Add a GDB pretty printer for base::flat_map.

tools/gdb/gdb_chrome.py

 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """GDB support for Chrome types.
 
 Add this to your gdb by amending your ~/.gdbinit as follows:
   python
   import sys
   sys.path.insert(0, "/path/to/tools/gdb/")
   import gdb_chrome
   end
 
 Use
   (gdb) p /r any_variable
 to print |any_variable| without using any printers.
+
+To interactively type Python for development of the printers:
+  (gdb) python foo = gdb.parse_and_eval('bar')
+to put the C++ value 'bar' in the current scope into a Python variable 'foo'.
+Then you can interact with that variable:
+  (gdb) python print foo['impl_']
 """
 
 import datetime
 import gdb
 import gdb.printing
 import os
 import sys
 
 sys.path.insert(0, os.path.join(
     os.path.dirname(os.path.abspath(__file__)),
@@ skipping 206 matching lines @@
 
 class ManualConstructorPrinter(object):
     def __init__(self, val):
         self.val = val
 
     def to_string(self):
         return self.val['space_'].cast(self.val.type.template_argument(0))
 pp_set.add_printer('base::ManualConstructor', '^base::ManualConstructor<.*>$', ManualConstructorPrinter)
 
 
+class FlatMapPrinter(object):
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        # It would be nice to match the output of std::map which is a little
+        # nicer than printing the vector of pairs. But iterating over it in
+        # Python is much more complicated and this output is reasonable.
+        # (Without this printer, a flat_map will output 7 lines of internal
+        # template goop before the vector contents.)
+        return 'base::flat_map with ' + str(self.val['impl_']['body_'])
+pp_set.add_printer('base::flat_map', '^base::flat_map<.*>$', FlatMapPrinter)
+
+
 class ValuePrinter(object):
     def __init__(self, val):
         self.val = val
 
     def get_type(self):
         return self.val['type_']
 
     def to_string(self):
         typestr = str(self.get_type())
         # Trim prefix to just get the emum short name.
@@ skipping 118 matching lines @@
         yield ('sudden_termination_allowed_',
                self.val['sudden_termination_allowed_'])
         yield ('ignore_input_events_', self.val['ignore_input_events_'])
         yield ('is_guest_', self.val['is_guest_'])
 pp_set.add_printer('content::RenderProcessHostImpl',
                    '^content::RenderProcessHostImpl$',
                    RenderProcessHostImplPrinter)
 
 
 gdb.printing.register_pretty_printer(gdb, pp_set, replace=_DEBUGGING)