Disable prerendering in single-process mode

Prerendering causes creation of additional RenderProcessHostImpl
objects, which hold it's own blink instance. In single-process mode this
causes blink to be initialized multiple times, which in turn triggers a
DCHECK "FATAL:platform.cc(180)] Check failed: !did_initialize_blink_."

This change disables prerendering in single-process mode.

Test: load http://jmajnert.github.io/tests/prerender_landing.html in
      debug single-process build

Bug: 1151372
Change-Id: I23992afbf681089b4b25e084eeccf470484b2320
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550560Reviewed-by: Robert Ogden <robertogden@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#830249}

chrome/browser/prefetch/no_state_prefetch/prerender_unittest.cc

@@ -46,6 +46,7 @@
 #include "components/no_state_prefetch/common/prerender_util.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/test/browser_task_environment.h"
 #include "content/public/test/test_utils.h"
 #include "mojo/public/cpp/bindings/unique_receiver_set.h"
@@ -1654,4 +1655,14 @@ TEST_F(PrerenderTest, PrerenderContentsIncrementsByteCount) {
   EXPECT_EQ(12, prerender_contents->network_bytes());
 }
 
+TEST_F(PrerenderTest, NoPrerenderInSingleProcess) {
+  GURL url("http://www.google.com/");
+  auto* command_line = base::CommandLine::ForCurrentProcess();
+  ASSERT_TRUE(command_line != nullptr);
+  command_line->AppendSwitch(switches::kSingleProcess);
+  EXPECT_FALSE(AddSimplePrerender(url));
+  histogram_tester().ExpectUniqueSample("Prerender.FinalStatus",
+                                        FINAL_STATUS_SINGLE_PROCESS, 1);
+}
+
 }  // namespace prerender

components/no_state_prefetch/browser/prerender_manager.cc

@@ -15,6 +15,7 @@
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/check_op.h"
+#include "base/command_line.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ -49,6 +50,7 @@
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_delegate.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/common/url_constants.h"
 #include "net/http/http_cache.h"
 #include "net/http/http_request_headers.h"
@@ -491,6 +493,13 @@ PrerenderManager::AddPrerenderWithPreconnectFallback(
     SessionStorageNamespace* session_storage_namespace) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line && command_line->HasSwitch(switches::kSingleProcess)) {
+    SkipPrerenderContentsAndMaybePreconnect(url_arg, origin,
+                                            FINAL_STATUS_SINGLE_PROCESS);
+    return nullptr;
+  }
+
   // Disallow prerendering on low end devices.
   if (IsLowEndDevice()) {
     SkipPrerenderContentsAndMaybePreconnect(url_arg, origin,
@@ -925,7 +934,7 @@ void PrerenderManager::SkipPrerenderContentsAndMaybePreconnect(
   }
 
   static_assert(
-      FINAL_STATUS_MAX == FINAL_STATUS_NAVIGATION_PREDICTOR_HOLDBACK + 1,
+      FINAL_STATUS_MAX == FINAL_STATUS_SINGLE_PROCESS + 1,
       "Consider whether a failed prerender should fallback to preconnect");
 }
 

components/no_state_prefetch/common/prerender_final_status.cc

@@ -74,6 +74,7 @@ const char* kFinalStatusNames[] = {
     "GWS Holdback",
     "Unknown",
     "Navigation Predictor Holdback",
+    "Single Process Mode",
     "Max",
 };
 static_assert(base::size(kFinalStatusNames) == FINAL_STATUS_MAX + 1,

components/no_state_prefetch/common/prerender_final_status.h

@@ -79,6 +79,7 @@ enum FinalStatus {
   FINAL_STATUS_GWS_HOLDBACK = 59,
   FINAL_STATUS_UNKNOWN = 60,
   FINAL_STATUS_NAVIGATION_PREDICTOR_HOLDBACK = 61,
+  FINAL_STATUS_SINGLE_PROCESS = 62,
   FINAL_STATUS_MAX,
 };
 
@@ -88,4 +89,4 @@ const char* NameFromFinalStatus(FinalStatus final_status);
 
 }  // namespace prerender
 
-#endif  // COMPONENTS_NO_STATE_PREFETCH_COMMON_PRERENDER_FINAL_STATUS_H_
\ No newline at end of file
+#endif  // COMPONENTS_NO_STATE_PREFETCH_COMMON_PRERENDER_FINAL_STATUS_H_