Expose a way to set a view's base background color.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index e525031ce93686e42f3caf18ad834c0a7c5ad6bd..acc2f8a8a9f01728edfe29b2b62b5b159d4934aa 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -138,7 +138,6 @@
 #include "core/platform/chromium/KeyboardCodes.h"
 #include "core/platform/chromium/TraceEvent.h"
 #include "core/platform/chromium/support/WebActiveGestureAnimation.h"
-#include "core/platform/graphics/Color.h"
 #include "core/platform/graphics/ColorSpace.h"
 #include "core/platform/graphics/Extensions3D.h"
 #include "core/platform/graphics/FontCache.h"
@@ -427,6 +426,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_showDebugBorders(false)
     , m_continuousPaintingEnabled(false)
     , m_showScrollBottleneckRects(false)
+    , m_baseBackgroundColor(Color::white)
 {
     Page::PageClients pageClients;
     pageClients.chromeClient = &m_chromeClientImpl;
@@ -2459,11 +2459,11 @@ WebColor WebViewImpl::backgroundColor() const
     if (isTransparent())
         return Color::transparent;
     if (!m_page)
-        return Color::white;
+        return m_baseBackgroundColor.rgb();
     FrameView* view = m_page->mainFrame()->view();
     Color backgroundColor = view->documentBackgroundColor();
     if (!backgroundColor.isValid())
-        return Color::white;
+        return m_baseBackgroundColor.rgb();
     return backgroundColor.rgb();
 }
 
@@ -3571,6 +3571,20 @@ void WebViewImpl::setIsTransparent(bool isTransparent)
     m_isTransparent = isTransparent;
 }
 
+void WebViewImpl::setBaseBackgroundColor(WebColor color)
+{
+    Color c(static_cast<RGBA32>(color));
+    if (m_baseBackgroundColor == c)
+        return;
+
+    m_baseBackgroundColor = c;
+
+    m_page->mainFrame()->view()->updateBackgroundRecursively(c, m_isTransparent);
+
+    if (m_layerTreeView)
+        m_layerTreeView->setBackgroundColor(backgroundColor());
+}
+
 bool WebViewImpl::isTransparent() const
 {
     return m_isTransparent;