Reland: Deprecate mojo::DataPipe

This is the first step in eliminating mojo::DataPipe. Marking it as
deprecated with a comment and adding a DLOG (that only logs once per
process launch) will hopefully stop it from being used in new code.

Previous change was reverted due to log spam.

Bug: 944990
Change-Id: I492f7ac2038db31ce4af6a31a0b1a80570c46aef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1544798
Auto-Submit: Carlos Knippschild <carlosk@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Commit-Queue: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#648821}

PRESUBMIT.py

@@ -710,6 +710,14 @@ _BANNED_CPP_FUNCTIONS = (
         r'^third_party/blink/renderer/.*\.(cc|h)$',
       ),
     ),
+    (
+      'mojo::DataPipe',
+      (
+        'mojo::DataPipe is deprecated. Use mojo::CreateDataPipe instead.',
+      ),
+      True,
+      (),
+    ),
 )
 
 

PRESUBMIT_test.py

@@ -1772,6 +1772,20 @@ class BannedFunctionCheckTest(unittest.TestCase):
     self.assertTrue('another/ios_file.mm' in errors[0].message)
     self.assertTrue('some/mac/file.mm' not in errors[0].message)
 
+  def testBannedMojoFunctions(self):
+    input_api = MockInputApi()
+    input_api.files = [
+      MockFile('some/cpp/problematic/file.cc',
+               ['mojo::DataPipe();']),
+      MockFile('some/cpp/ok/file.cc',
+               ['CreateDataPipe();']),
+    ]
+
+    errors = PRESUBMIT._CheckNoBannedFunctions(input_api, MockOutputApi())
+    self.assertEqual(1, len(errors))
+    self.assertTrue('some/cpp/problematic/file.cc' in errors[0].message)
+    self.assertTrue('some/cpp/ok/file.cc' not in errors[0].message)
+
 
 class NoProductionCodeUsingTestOnlyFunctionsTest(unittest.TestCase):
   def testTruePositives(self):

mojo/public/cpp/system/data_pipe.h

@@ -131,16 +131,12 @@ inline MojoResult CreateDataPipe(
   return rv;
 }
 
+// DEPRECATED: use |CreateDataPipe| instead.
+//
+// This class is not safe to use in production code as there is no way for it to
+// report failure while creating the pipe and it will CHECK in case of failures.
+//
 // A wrapper class that automatically creates a data pipe and owns both handles.
-//
-// Note that this class is not safe to use in production code, as there is no
-// way for it to report failure while creating the pipe, while in practice
-// creating a new data pipe does fail every now and then. Instead just call
-// CreateDataPipe directly and check its return value.
-//
-// TODO(vtl): Make an even more friendly version? (Maybe templatized for a
-// particular type instead of some "element"? Maybe functions that take
-// vectors?)
 class MOJO_CPP_SYSTEM_EXPORT DataPipe {
  public:
   DataPipe();