Upstream the iOS web_shell and supporting code

ios/web/shell/MainView.xib

Index: ios/web/shell/MainView.xib
diff --git a/ios/web/shell/MainView.xib b/ios/web/shell/MainView.xib
new file mode 100644
index 0000000000000000000000000000000000000000..00cea73307092afb9499ffc1ae6f74292a709ef2
--- /dev/null
+++ b/ios/web/shell/MainView.xib
@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="5053" systemVersion="13D65" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none">
+    <dependencies>
+        <deployment version="1552" identifier="iOS"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="3733"/>
+    </dependencies>
+    <objects>
+        <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner" customClass="ViewController">
+            <connections>
+                <outlet property="containerView" destination="HS4-2y-YS7" id="KRU-Lk-zhW"/>
+                <outlet property="toolbarView" destination="Mtt-2S-TM5" id="Ngt-zy-T1l"/>
+                <outlet property="view" destination="iN0-l3-epB" id="0A6-5l-qvv"/>
+            </connections>
+        </placeholder>
+        <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
+        <view contentMode="scaleToFill" id="iN0-l3-epB">
+            <rect key="frame" x="0.0" y="0.0" width="320" height="568"/>
+            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+            <subviews>
+                <toolbar opaque="NO" clearsContextBeforeDrawing="NO" contentMode="scaleToFill" id="Mtt-2S-TM5">
+                    <rect key="frame" x="0.0" y="20" width="320" height="44"/>
+                    <autoresizingMask key="autoresizingMask" widthSizable="YES" flexibleMaxY="YES"/>
+                    <inset key="insetFor6xAndEarlier" minX="0.0" minY="20" maxX="0.0" maxY="-20"/>
+                    <items/>
+                    <color key="barTintColor" red="0.33725490196078434" green="0.46666666666666667" blue="0.9882352941176471" alpha="1" colorSpace="calibratedRGB"/>
+                    <connections>
+                        <outlet property="delegate" destination="-1" id="80Y-wy-gHw"/>
+                    </connections>
+                </toolbar>
+                <view contentMode="scaleToFill" id="HS4-2y-YS7">
+                    <rect key="frame" x="0.0" y="64" width="320" height="504"/>
+                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                    <color key="backgroundColor" white="0.66666666666666663" alpha="1" colorSpace="calibratedWhite"/>
+                    <inset key="insetFor6xAndEarlier" minX="0.0" minY="20" maxX="0.0" maxY="0.0"/>
+                </view>
+            </subviews>
+            <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
+            <simulatedStatusBarMetrics key="simulatedStatusBarMetrics"/>
+            <simulatedScreenMetrics key="simulatedDestinationMetrics" type="retina4"/>
+            <inset key="insetFor6xAndEarlier" minX="0.0" minY="0.0" maxX="0.0" maxY="-20"/>
+        </view>
+    </objects>
+</document>