Show guest WebContents in DevTools if possible

Chrome's DevTools has different behavior for PDF content:
- If it was opened for the PDF viewer, it closes itself when the
guest view has gone (e.g. by navigating away), but it shows the
inner content of the plugin.
- If it was opened for another site and then navigated to the PDF
plugin it won't show the inner content, but the embedding HTML of
the parent and it allows navigating away from the plugin.

Make our inspector match the behavior of Chrome and allow DevTools
to look into the plugin. It helps debugging PDF viewer related
issues.

Change-Id: I218d4fcf47d6b1f0101fa1d7f36758e04a1dd7b0
Reviewed-by: Anu Aliyas <anu.aliyas@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
(cherry picked from commit 6acf981aae2165cde6829f309f3792fc34852fd2)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit c503b50b189c7446b91edfede083100b206370fb)

3 files changed, 11 insertions, 2 deletions

diff --git a/src/core/devtools_frontend_qt.cpp b/src/core/devtools_frontend_qt.cpp
index 047026826..ff0596a3d 100644
--- a/src/core/devtools_frontend_qt.cpp
+++ b/src/core/devtools_frontend_qt.cpp
@@ -78,6 +78,7 @@ DevToolsFrontendQt::DevToolsFrontendQt(QSharedPointer<WebContentsAdapter> webCon
     : content::WebContentsObserver(webContentsAdapter->webContents())
     , m_frontendAdapter(webContentsAdapter)
     , m_inspectedContents(inspectedContents)
+    , m_outermostContents(inspectedContents->GetOutermostWebContents())
     , m_bindings(new DevToolsUIBindings(webContentsAdapter->webContents()))
 {
     // bindings take ownership over devtools
@@ -147,8 +148,10 @@ void DevToolsFrontendQt::ColorPickedInEyeDropper(int r, int g, int b, int a)
 // content::WebContentsObserver implementation
 void DevToolsFrontendQt::WebContentsDestroyed()
 {
+    // If m_inspectedContents was a guest view it was probably already destroyed,
+    // but its embedder still lives.
     WebContentsAdapter *inspectedAdapter =
-            static_cast<WebContentsDelegateQt *>(m_inspectedContents->GetDelegate())
+            static_cast<WebContentsDelegateQt *>(m_outermostContents->GetDelegate())
                     ->webContentsAdapter();
     if (inspectedAdapter)
         inspectedAdapter->devToolsFrontendDestroyed(this);
@@ -201,6 +204,8 @@ bool DevToolsFrontendQt::IsValidFrontendURL(const GURL &url)
 
 void DevToolsFrontendQt::InspectedContentsClosing()
 {
+    // Called for already destroyed guest views
+    m_inspectedContents = nullptr;
     web_contents()->ClosePage();
 }
 
diff --git a/src/core/devtools_frontend_qt.h b/src/core/devtools_frontend_qt.h
index ec7ccce83..b867d4af1 100644
--- a/src/core/devtools_frontend_qt.h
+++ b/src/core/devtools_frontend_qt.h
@@ -76,6 +76,7 @@ private:
     // We shouldn't be keeping it alive
     QWeakPointer<WebContentsAdapter> m_frontendAdapter;
     content::WebContents *m_inspectedContents;
+    content::WebContents *m_outermostContents;
     std::unique_ptr<DevToolsEyeDropper> m_eyeDropper;
     DevToolsUIBindings *m_bindings;
 };
diff --git a/src/core/web_contents_adapter.cpp b/src/core/web_contents_adapter.cpp
index f44675171..0f1162b25 100644
--- a/src/core/web_contents_adapter.cpp
+++ b/src/core/web_contents_adapter.cpp
@@ -1272,7 +1272,10 @@ void WebContentsAdapter::openDevToolsFrontend(QSharedPointer<WebContentsAdapter>
 
     setLifecycleState(LifecycleState::Active);
 
-    m_devToolsFrontend = DevToolsFrontendQt::Show(frontendAdapter, m_webContents.get());
+    content::WebContents *webContents = m_webContents.get();
+    if (content::WebContents *guest = guestWebContents())
+        webContents = guest;
+    m_devToolsFrontend = DevToolsFrontendQt::Show(frontendAdapter, webContents);
     updateRecommendedState();
 }