Bug 1197824 - Add a zoom-constraints-updated message. r=snorp

With this patch the ZoomConstraintsClient updates get broadcast via the observer
service on Android, allowing code in browser.js to switch over to using it.

--HG--
extra : commitid : FZvsgS8s2oT

widget/android/nsWindow.cpp

@@ -27,6 +27,7 @@ using mozilla::unused;
 
 #include "nsAppShell.h"
 #include "nsIdleService.h"
+#include "nsLayoutUtils.h"
 #include "nsWindow.h"
 #include "nsIObserverService.h"
 #include "nsFocusManager.h"
@@ -2541,3 +2542,34 @@ nsWindow::GetMaxTouchPoints() const
 {
     return GeckoAppShell::GetMaxTouchPoints();
 }
+
+void
+nsWindow::UpdateZoomConstraints(const uint32_t& aPresShellId,
+                                const FrameMetrics::ViewID& aViewId,
+                                const mozilla::Maybe<ZoomConstraints>& aConstraints)
+{
+#ifdef MOZ_ANDROID_APZ
+    nsBaseWidget::UpdateZoomConstraints(aPresShellId, aViewId, aConstraints);
+#else
+    if (!aConstraints) {
+        // This is intended to "clear" previously stored constraints but in our
+        // case we don't need to bother since they'll get GC'd from browser.js
+        return;
+    }
+    nsIContent* content = nsLayoutUtils::FindContentFor(aViewId);
+    nsIDocument* doc = content ? content->GetComposedDoc() : nullptr;
+    if (!doc) {
+        return;
+    }
+    nsCOMPtr<nsIObserverService> obsServ = mozilla::services::GetObserverService();
+    nsPrintfCString json("{ \"allowZoom\": %s,"
+                         "  \"allowDoubleTapZoom\": %s,"
+                         "  \"minZoom\": %f,"
+                         "  \"maxZoom\": %f }",
+        aConstraints->mAllowZoom ? "true" : "false",
+        aConstraints->mAllowDoubleTapZoom ? "true" : "false",
+        aConstraints->mMinZoom.scale, aConstraints->mMaxZoom.scale);
+    obsServ->NotifyObservers(doc, "zoom-constraints-updated",
+        NS_ConvertASCIItoUTF16(json.get()).get());
+#endif
+}

widget/android/nsWindow.h

@@ -169,6 +169,10 @@ public:
 
     virtual uint32_t GetMaxTouchPoints() const override;
 
+    void UpdateZoomConstraints(const uint32_t& aPresShellId,
+                               const FrameMetrics::ViewID& aViewId,
+                               const mozilla::Maybe<ZoomConstraints>& aConstraints) override;
+
 protected:
     void BringToFront();
     nsWindow *FindTopLevel();