Avoid reinitializing IdentifiabilityStudySettings in single process

Don't initialize the process-global IdentifiabilityStudySettings from
the renderer if in single-process mode. This makes it possible to run
debug chromium in single-process.

Bug: 1128395
Change-Id: I06b0fefd00d4bae48e090378526fbdafcfc8990c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2551127
Reviewed-by: Asanka Herath <asanka@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829714}

AUTHORS

@@ -442,6 +442,7 @@ James Wei <james.wei@intel.com>
 James Willcox <jwillcox@litl.com>
 Jan Rucka <ruckajan10@gmail.com>
 Jan Sauer <jan@jansauer.de>
+Janusz Majnert <jmajnert@gmail.com>
 Janwar Dinata <j.dinata@gmail.com>
 Jared Shumway <jaredshumway94@gmail.com>
 Jared Sohn <jared.sohn@gmail.com>

chrome/renderer/chrome_content_renderer_client.cc

@@ -440,18 +440,19 @@ void ChromeContentRendererClient::RenderThreadStarted() {
         WebString::FromASCII(scheme));
   }
 
-  // This doesn't work in single-process mode.
   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kSingleProcess)) {
+    // This doesn't work in single-process mode.
     ThreadProfiler::SetMainThreadTaskRunner(
         base::ThreadTaskRunnerHandle::Get());
     mojo::PendingRemote<metrics::mojom::CallStackProfileCollector> collector;
     thread->BindHostReceiver(collector.InitWithNewPipeAndPassReceiver());
     ThreadProfiler::SetCollectorForChildProcess(std::move(collector));
-  }
 
-  blink::IdentifiabilityStudySettings::SetGlobalProvider(
-      std::make_unique<PrivacyBudgetSettingsProvider>());
+    // This is superfluous in single-process mode and triggers a DCHECK
+    blink::IdentifiabilityStudySettings::SetGlobalProvider(
+        std::make_unique<PrivacyBudgetSettingsProvider>());
+  }
 }
 
 void ChromeContentRendererClient::ExposeInterfacesToBrowser(