fix references to zygote_host_linux.cc

Commit a042173: ("Move the rest of the core files in chrome\browser
to content\browser.") moved it from chrome/browser/zygote_host_linux.cc
to content/browser/zygote_host_linux.cc.

Commit c2c68b1: ("Add an API around zygoteHost so that chrome doesn't
reach into the internal content implementation.") renamed it from
content/browser/zygote_host_linux.cc to content/browser/zygote_host_impl_linux.cc.

Commit 13d6b3c: ("Move zygote_host_impl_linux.* to content/browser/zygote_host")
moved it into content/browser/zygote_host.

BUG=None

Change-Id: Ie8f8fad945ec53109f67cf53462cd4af01c70d44
Reviewed-on: https://chromium-review.googlesource.com/509248
Commit-Queue: Thiago Farina <tfarina@chromium.org>
Reviewed-by: Ricky Zhou <rickyz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#474641}

content/zygote/zygote_linux.cc

@@ -125,7 +125,8 @@ bool Zygote::ProcessRequests() {
 
   if (UsingSUIDSandbox() || UsingNSSandbox()) {
     // Let the ZygoteHost know we are ready to go.
-    // The receiving code is in content/browser/zygote_host_linux.cc.
+    // The receiving code is in
+    // content/browser/zygote_host/zygote_host_impl_linux.cc.
     bool r = base::UnixDomainSocket::SendMsg(kZygoteSocketPairFd,
                                              kZygoteHelloMessage,
                                              sizeof(kZygoteHelloMessage),

docs/linux_zygote.md

@@ -36,7 +36,7 @@ randomisation than the browser.
 
 The zygote process is triggered by the `--type=zygote` command line flag, which
 causes `ZygoteMain` (in `chrome/browser/zygote_main_linux.cc`) to be run. The
-zygote is launched from `chrome/browser/zygote_host_linux.cc`.
+zygote is launched from `content/browser/zygote_host/zygote_host_impl_linux.cc`.
 
 Signaling the zygote for a new renderer happens in
 `chrome/browser/child_process_launcher.cc`.

sandbox/linux/suid/sandbox.c

@@ -353,10 +353,10 @@ static bool SetupChildEnvironment() {
   unsigned i;
 
   // ld.so may have cleared several environment variables because we are SUID.
-  // However, the child process might need them so zygote_host_linux.cc saves a
-  // copy in SANDBOX_$x. This is safe because we have dropped root by this
-  // point, so we can only exec a binary with the permissions of the user who
-  // ran us in the first place.
+  // However, the child process might need them so zygote_host_impl_linux.cc
+  // saves a copy in SANDBOX_$x. This is safe because we have dropped root by
+  // this point, so we can only exec a binary with the permissions of the user
+  // who ran us in the first place.
 
   for (i = 0; kSUIDUnsafeEnvironmentVariables[i]; ++i) {
     const char* const envvar = kSUIDUnsafeEnvironmentVariables[i];