[DevTools] Check that mainFrameImpl() has been initalized before accessing it.

third_party/WebKit/Source/web/DevToolsEmulator.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "web/DevToolsEmulator.h"
 
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/page/Page.h"
@@ skipping 211 matching lines @@
 
     m_webViewImpl->page()->settings().setDeviceScaleAdjustment(calculateDeviceScaleAdjustment(params.viewSize.width, params.viewSize.height, params.deviceScaleFactor));
 
     if (params.screenPosition == WebDeviceEmulationParams::Mobile)
         enableMobileEmulation();
     else
         disableMobileEmulation();
 
     m_webViewImpl->setCompositorDeviceScaleFactorOverride(params.deviceScaleFactor);
     m_webViewImpl->setRootLayerTransform(WebSize(params.offset.x, params.offset.y), params.scale);
-    if (Document* document = m_webViewImpl->mainFrameImpl()->frame()->document())
-        document->mediaQueryAffectingValueChanged();
+    // TODO(dgozman): mainFrameImpl() is null when it's remote. Figure out how
+    // we end up with enabling emulation in this case.
+    if (m_webViewImpl->mainFrameImpl()) {
+        if (Document* document = m_webViewImpl->mainFrameImpl()->frame()->document())
+            document->mediaQueryAffectingValueChanged();
+    }
 }
 
 void DevToolsEmulator::disableDeviceEmulation()
 {
     if (!m_deviceMetricsEnabled)
         return;
 
     m_deviceMetricsEnabled = false;
     m_webViewImpl->setBackgroundColorOverride(Color::transparent);
     m_webViewImpl->updateShowFPSCounter();
     m_webViewImpl->page()->settings().setDeviceScaleAdjustment(m_embedderDeviceScaleAdjustment);
     disableMobileEmulation();
     m_webViewImpl->setCompositorDeviceScaleFactorOverride(0.f);
     m_webViewImpl->setRootLayerTransform(WebSize(0.f, 0.f), 1.f);
     m_webViewImpl->setPageScaleFactor(1.f);
-    if (Document* document = m_webViewImpl->mainFrameImpl()->frame()->document())
-        document->mediaQueryAffectingValueChanged();
+    // mainFrameImpl() could be null during cleanup or remote <-> local swap.
+    if (m_webViewImpl->mainFrameImpl()) {
+        if (Document* document = m_webViewImpl->mainFrameImpl()->frame()->document())
+            document->mediaQueryAffectingValueChanged();
+    }
 }
 
 bool DevToolsEmulator::resizeIsDeviceSizeChange()
 {
     return m_deviceMetricsEnabled && m_emulateMobileEnabled;
 }
 
 void DevToolsEmulator::enableMobileEmulation()
 {
     if (m_emulateMobileEnabled)
@@ skipping 12 matching lines @@
     m_webViewImpl->page()->settings().setAvailablePointerTypes(PointerTypeCoarse);
     m_webViewImpl->page()->settings().setPrimaryPointerType(PointerTypeCoarse);
     m_webViewImpl->page()->settings().setAvailableHoverTypes(HoverTypeOnDemand);
     m_webViewImpl->page()->settings().setPrimaryHoverType(HoverTypeOnDemand);
     m_webViewImpl->page()->settings().setResizeIsDeviceSizeChange(true);
     m_webViewImpl->setZoomFactorOverride(1);
 
     m_originalDefaultMinimumPageScaleFactor = m_webViewImpl->defaultMinimumPageScaleFactor();
     m_originalDefaultMaximumPageScaleFactor = m_webViewImpl->defaultMaximumPageScaleFactor();
     m_webViewImpl->setDefaultPageScaleLimits(0.25f, 5);
-    m_webViewImpl->mainFrameImpl()->frameView()->layout();
+    // TODO(dgozman): mainFrameImpl() is null when it's remote. Figure out how
+    // we end up with enabling emulation in this case.
+    if (m_webViewImpl->mainFrameImpl())
+        m_webViewImpl->mainFrameImpl()->frameView()->layout();
 }
 
 void DevToolsEmulator::disableMobileEmulation()
 {
     if (!m_emulateMobileEnabled)
         return;
     RuntimeEnabledFeatures::setOverlayScrollbarsEnabled(m_isOverlayScrollbarsEnabled);
     m_webViewImpl->disableViewport();
     m_webViewImpl->settings()->setViewportMetaEnabled(false);
     m_webViewImpl->page()->frameHost().visualViewport().initializeScrollbars();
     m_webViewImpl->settings()->setShrinksViewportContentToFit(false);
     m_webViewImpl->page()->settings().setTextAutosizingEnabled(m_embedderTextAutosizingEnabled);
     m_webViewImpl->page()->settings().setPreferCompositingToLCDTextEnabled(m_embedderPreferCompositingToLCDTextEnabled);
     m_webViewImpl->page()->settings().setUseMobileViewportStyle(m_embedderUseMobileViewport);
     m_webViewImpl->page()->settings().setPluginsEnabled(m_embedderPluginsEnabled);
     m_webViewImpl->page()->settings().setAvailablePointerTypes(m_embedderAvailablePointerTypes);
     m_webViewImpl->page()->settings().setPrimaryPointerType(m_embedderPrimaryPointerType);
     m_webViewImpl->page()->settings().setAvailableHoverTypes(m_embedderAvailableHoverTypes);
     m_webViewImpl->page()->settings().setPrimaryHoverType(m_embedderPrimaryHoverType);
     m_webViewImpl->page()->settings().setResizeIsDeviceSizeChange(false);
     m_webViewImpl->setZoomFactorOverride(0);
     m_emulateMobileEnabled = false;
     m_webViewImpl->setDefaultPageScaleLimits(
         m_originalDefaultMinimumPageScaleFactor,
         m_originalDefaultMaximumPageScaleFactor);
-    m_webViewImpl->mainFrameImpl()->frameView()->layout();
+    // mainFrameImpl() could be null during cleanup or remote <-> local swap.
+    if (m_webViewImpl->mainFrameImpl())
+        m_webViewImpl->mainFrameImpl()->frameView()->layout();
 }
 
 void DevToolsEmulator::setTouchEventEmulationEnabled(bool enabled)
 {
     if (m_touchEventEmulationEnabled == enabled)
         return;
     if (!m_touchEventEmulationEnabled) {
         m_originalTouchEnabled = RuntimeEnabledFeatures::touchEnabled();
         m_originalDeviceSupportsMouse = m_webViewImpl->page()->settings().deviceSupportsMouse();
         m_originalDeviceSupportsTouch = m_webViewImpl->page()->settings().deviceSupportsTouch();
         m_originalMaxTouchPoints = m_webViewImpl->page()->settings().maxTouchPoints();
     }
     RuntimeEnabledFeatures::setTouchEnabled(enabled ? true : m_originalTouchEnabled);
     if (!m_originalDeviceSupportsTouch) {
         m_webViewImpl->page()->settings().setDeviceSupportsMouse(enabled ? false : m_originalDeviceSupportsMouse);
         m_webViewImpl->page()->settings().setDeviceSupportsTouch(enabled ? true : m_originalDeviceSupportsTouch);
         // Currently emulation does not provide multiple touch points.
         m_webViewImpl->page()->settings().setMaxTouchPoints(enabled ? 1 : m_originalMaxTouchPoints);
     }
     m_touchEventEmulationEnabled = enabled;
-    m_webViewImpl->mainFrameImpl()->frameView()->layout();
+    // TODO(dgozman): mainFrameImpl() check in this class should be unnecessary.
+    // It is only needed when we reattach and restore InspectorEmulationAgent,
+    // which happens before everything has been setup correctly, and therefore
+    // fails during remote -> local main frame transition.
+    // We should instead route emulation from browser through the WebViewImpl
+    // to the local main frame, and remove InspectorEmulationAgent entirely.
+    if (m_webViewImpl->mainFrameImpl())
+        m_webViewImpl->mainFrameImpl()->frameView()->layout();
 }
 
 void DevToolsEmulator::setScriptExecutionDisabled(bool scriptExecutionDisabled)
 {
     m_scriptExecutionDisabled = scriptExecutionDisabled;
     m_webViewImpl->page()->settings().setScriptEnabled(m_scriptExecutionDisabled ? false : m_embedderScriptEnabled);
 }
 
 bool DevToolsEmulator::handleInputEvent(const WebInputEvent& inputEvent)
 {
@@ skipping 24 matching lines @@
             m_lastPinchAnchorCss.clear();
             m_lastPinchAnchorDip.clear();
         }
         return true;
     }
 
     return false;
 }
 
 } // namespace blink