Make <meter> transparent if -webkit-appearance:none or background CSS property is specified.

third_party/WebKit/Source/core/html/shadow/MeterShadowElement.h

Index: third_party/WebKit/Source/core/html/shadow/MeterShadowElement.h
diff --git a/third_party/WebKit/Source/core/html/shadow/MeterShadowElement.h b/third_party/WebKit/Source/core/html/shadow/MeterShadowElement.h
index 198f2e72398cfb7696bda284cc418522cad5d360..04fda3ebc6ddf91d735b6f21bb5facc255cdf80c 100644
--- a/third_party/WebKit/Source/core/html/shadow/MeterShadowElement.h
+++ b/third_party/WebKit/Source/core/html/shadow/MeterShadowElement.h
@@ -38,6 +38,15 @@ namespace blink {
 
 class HTMLMeterElement;
 
+class MeterFallbackElement : public HTMLDivElement {
+public:
+    DECLARE_NODE_FACTORY(MeterFallbackElement);
+
+private:
+    explicit MeterFallbackElement(Document&);
+    PassRefPtr<ComputedStyle> customStyleForLayoutObject() override;
+};
+
 class MeterShadowElement : public HTMLDivElement {
 protected:
     explicit MeterShadowElement(Document&);
@@ -55,6 +64,7 @@ private:
     explicit MeterInnerElement(Document&);
     bool layoutObjectIsNeeded(const ComputedStyle&) override;
     LayoutObject* createLayoutObject(const ComputedStyle&) override;
+    PassRefPtr<ComputedStyle> customStyleForLayoutObject() override;
 };
 
 class MeterBarElement final : public MeterShadowElement {