Break dependence of zygote_linux.cc on common_sandbox_support_linux.h

Content's zygote_main should be responsible for communicating an
additional argument as required to keep zygote_linux.h ignorant.

Change-Id: I475f0eee5c200f536154c4f847b39d731d0e77f1
Reviewed-on: https://chromium-review.googlesource.com/862612
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529929}

content/zygote/zygote_linux.cc

@@ -33,7 +33,6 @@
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "content/common/zygote_commands_linux.h"
-#include "content/public/common/common_sandbox_support_linux.h"
 #include "content/public/common/content_descriptors.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/mojo_channel_switches.h"
@@ -95,16 +94,17 @@ void KillAndReap(pid_t pid, ZygoteForkDelegate* helper) {
 Zygote::Zygote(int sandbox_flags,
                std::vector<std::unique_ptr<ZygoteForkDelegate>> helpers,
                const std::vector<base::ProcessHandle>& extra_children,
-               const std::vector<int>& extra_fds)
+               const std::vector<int>& extra_fds,
+               const base::GlobalDescriptors::Descriptor& ipc_backchannel)
     : sandbox_flags_(sandbox_flags),
       helpers_(std::move(helpers)),
       initial_uma_index_(0),
       extra_children_(extra_children),
       extra_fds_(extra_fds),
-      to_reap_() {}
+      to_reap_(),
+      ipc_backchannel_(ipc_backchannel) {}
 
-Zygote::~Zygote() {
-}
+Zygote::~Zygote() {}
 
 bool Zygote::ProcessRequests() {
   // A SOCK_SEQPACKET socket is installed in fd 3. We get commands from the
@@ -610,8 +610,7 @@ base::ProcessId Zygote::ReadArgsAndFork(base::PickleIterator iter,
     mapping.push_back(base::GlobalDescriptors::Descriptor(key, fds[i].get()));
   }
 
-  mapping.push_back(base::GlobalDescriptors::Descriptor(
-      static_cast<uint32_t>(kSandboxIPCChannel), GetSandboxFD()));
+  mapping.push_back(ipc_backchannel_);
 
   // Returns twice, once per process.
   base::ProcessId child_pid =

content/zygote/zygote_linux.h

@@ -35,7 +35,8 @@ class Zygote {
   Zygote(int sandbox_flags,
          std::vector<std::unique_ptr<ZygoteForkDelegate>> helpers,
          const std::vector<base::ProcessHandle>& extra_children,
-         const std::vector<int>& extra_fds);
+         const std::vector<int>& extra_fds,
+         const base::GlobalDescriptors::Descriptor& ipc_backchannel);
   ~Zygote();
 
   bool ProcessRequests();
@@ -153,6 +154,10 @@ class Zygote {
 
   // The vector contains the child processes that need to be reaped.
   std::vector<ZygoteProcessInfo> to_reap_;
+
+  // Sandbox IPC channel for renderers to invoke services from the browser. See
+  // https://chromium.googlesource.com/chromium/src/+/master/docs/linux_sandbox_ipc.md
+  base::GlobalDescriptors::Descriptor ipc_backchannel_;
 };
 
 }  // namespace content

content/zygote/zygote_main_linux.cc

@@ -37,6 +37,7 @@
 #include "content/common/font_config_ipc_linux.h"
 #include "content/common/zygote_commands_linux.h"
 #include "content/public/common/common_sandbox_support_linux.h"
+#include "content/public/common/content_descriptors.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/main_function_params.h"
 #include "content/public/common/zygote_fork_delegate_linux.h"
@@ -633,7 +634,10 @@ bool ZygoteMain(
   CHECK_EQ(using_namespace_sandbox, namespace_sandbox_engaged);
 
   Zygote zygote(sandbox_flags, std::move(fork_delegates), extra_children,
-                extra_fds);
+                extra_fds,
+                base::GlobalDescriptors::Descriptor(
+                    static_cast<uint32_t>(kSandboxIPCChannel), GetSandboxFD()));
+
   // This function call can return multiple times, once per fork().
   return zygote.ProcessRequests();
 }