Add hooks for BeforeInstallPromptEvent to be redispatched.

Source/modules/app_banner/BeforeInstallPromptEvent.cpp

Index: Source/modules/app_banner/BeforeInstallPromptEvent.cpp
diff --git a/Source/modules/app_banner/BeforeInstallPromptEvent.cpp b/Source/modules/app_banner/BeforeInstallPromptEvent.cpp
index a11e7cd5a000f3bdb356628b4544d541f294dc86..4b9df061afcd3a32979b359c614712c73d0cee16 100644
--- a/Source/modules/app_banner/BeforeInstallPromptEvent.cpp
+++ b/Source/modules/app_banner/BeforeInstallPromptEvent.cpp
@@ -22,6 +22,7 @@ BeforeInstallPromptEvent::BeforeInstallPromptEvent(const AtomicString& name, con
     , m_platforms(platforms)
     , m_requestId(requestId)
     , m_client(client)
+    , m_redispatched(false)
 {
 }
 
@@ -30,6 +31,7 @@ BeforeInstallPromptEvent::BeforeInstallPromptEvent(const AtomicString& name, con
     , m_platforms(init.platforms())
     , m_requestId(-1)
     , m_client(nullptr)
+    , m_redispatched(false)
 {
 }
 
@@ -59,4 +61,16 @@ const AtomicString& BeforeInstallPromptEvent::interfaceName() const
     return EventNames::BeforeInstallPromptEvent;
 }
 
+void BeforeInstallPromptEvent::prompt()
+{
+    // This will silently fail if preventDefault() has not previously been
+    // called (the event cannot be redispatched if it has not been stopped).
+    // It will also silently fail if the event has already been redispatched.

[mlamouri (slow - plz ping), 2015/06/06 21:40:55]

Why silently failing? Why not having prompt() return a Promise<> and reject the
promise if the state isn't the expected one? It will also give leeway for UA to
reject the prompt() request.

+    if (m_client && defaultPrevented() && !m_redispatched) {
+        ASSERT(m_requestId != -1);
+        m_redispatched = true;
+        m_client->resolveEventRedispatch(m_requestId);
+    }
+}
+
 } // namespace blink