Switch to LayoutThemeMobile when emulating mobile device in DevTools.

third_party/WebKit/Source/web/DevToolsEmulator.cpp

Index: third_party/WebKit/Source/web/DevToolsEmulator.cpp
diff --git a/third_party/WebKit/Source/web/DevToolsEmulator.cpp b/third_party/WebKit/Source/web/DevToolsEmulator.cpp
index bdf02329725645f88ae76bcdf9d2dccc50ff89b3..9b556bd6c9ae1f1b09a2ca7279eef0b0c11ede88 100644
--- a/third_party/WebKit/Source/web/DevToolsEmulator.cpp
+++ b/third_party/WebKit/Source/web/DevToolsEmulator.cpp
@@ -8,6 +8,7 @@
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/page/Page.h"
+#include "core/style/ComputedStyle.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "public/platform/WebLayerTreeView.h"
 #include "web/WebInputEventConversion.h"
@@ -51,6 +52,7 @@ DevToolsEmulator::DevToolsEmulator(WebViewImpl* webViewImpl)
     , m_deviceMetricsEnabled(false)
     , m_emulateMobileEnabled(false)
     , m_isOverlayScrollbarsEnabled(false)
+    , m_isMobileLayoutThemeEnabled(false)
     , m_originalDefaultMinimumPageScaleFactor(0)
     , m_originalDefaultMaximumPageScaleFactor(0)
     , m_embedderTextAutosizingEnabled(webViewImpl->page()->settings().textAutosizingEnabled())
@@ -255,6 +257,9 @@ void DevToolsEmulator::enableMobileEmulation()
     m_emulateMobileEnabled = true;
     m_isOverlayScrollbarsEnabled = RuntimeEnabledFeatures::overlayScrollbarsEnabled();
     RuntimeEnabledFeatures::setOverlayScrollbarsEnabled(true);
+    m_isMobileLayoutThemeEnabled = RuntimeEnabledFeatures::mobileLayoutThemeEnabled();
+    RuntimeEnabledFeatures::setMobileLayoutThemeEnabled(true);
+    ComputedStyle::clearInitialStyle();
     m_webViewImpl->page()->settings().setUseMobileViewportStyle(true);
     m_webViewImpl->enableViewport();
     m_webViewImpl->settings()->setViewportMetaEnabled(true);
@@ -284,6 +289,8 @@ void DevToolsEmulator::disableMobileEmulation()
     if (!m_emulateMobileEnabled)
         return;
     RuntimeEnabledFeatures::setOverlayScrollbarsEnabled(m_isOverlayScrollbarsEnabled);
+    RuntimeEnabledFeatures::setMobileLayoutThemeEnabled(m_isMobileLayoutThemeEnabled);
+    ComputedStyle::clearInitialStyle();
     m_webViewImpl->disableViewport();
     m_webViewImpl->settings()->setViewportMetaEnabled(false);
     m_webViewImpl->page()->frameHost().visualViewport().initializeScrollbars();