Android: Get rid of extra dup()s on launching child processes

This is a regression from [1] which added a dup() call on
the renderer launching process. This CL removes these calls
by reveiling the subtle ownership of the file descriptors.

The original intention here was to completely hide and simplify
the notion of the ownership, at the cost of a few dup() calls.
However, the crash report on the reported bug indicates that
the dup() can fail and it lets the renderer initialization fail,
probably due to some per-process limit of the number of opened files.

[1] https://codereview.chromium.org/585203002

R=mdempsky@chromium.org, jam@chromium.org
BUG=455364

Review URL: https://codereview.chromium.org/909553003

Cr-Commit-Position: refs/heads/master@{#315353}

1 files changed, 21 insertions, 0 deletions

diff --git a/content/browser/file_descriptor_info_impl.cc b/content/browser/file_descriptor_info_impl.cc
index c1f055b..45ce542 100644
--- a/content/browser/file_descriptor_info_impl.cc
+++ b/content/browser/file_descriptor_info_impl.cc
@@ -47,6 +47,27 @@ bool FileDescriptorInfoImpl::HasID(int id) const {
   return false;
 }
 
+bool FileDescriptorInfoImpl::OwnsFD(base::PlatformFile file) const {
+  return owned_descriptors_.end() !=
+         std::find_if(
+             owned_descriptors_.begin(), owned_descriptors_.end(),
+             [file](const base::ScopedFD* fd) { return fd->get() == file; });
+}
+
+base::ScopedFD FileDescriptorInfoImpl::ReleaseFD(base::PlatformFile file) {
+  DCHECK(OwnsFD(file));
+
+  base::ScopedFD fd;
+  auto found = std::find_if(
+      owned_descriptors_.begin(), owned_descriptors_.end(),
+      [file](const base::ScopedFD* fd) { return fd->get() == file; });
+
+  (*found)->swap(fd);
+  owned_descriptors_.erase(found);
+
+  return fd.Pass();
+}
+
 void FileDescriptorInfoImpl::AddToMapping(int id, base::PlatformFile fd) {
   DCHECK(!HasID(id));
   mapping_.push_back(std::make_pair(fd, id));