diff --git a/extensions/chromium/pdfHandler.js b/extensions/chromium/pdfHandler.js
index 38e3b09c1..95f55732a 100644
--- a/extensions/chromium/pdfHandler.js
+++ b/extensions/chromium/pdfHandler.js
@@ -252,6 +252,32 @@ chrome.extension.isAllowedFileSchemeAccess(function(isAllowedAccess) {
 });
 
 chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
+  if (message && message.action === 'getParentOrigin') {
+    // getParentOrigin is used to determine whether it is safe to embed a
+    // sensitive (local) file in a frame.
+    if (!sender.tab) {
+      sendResponse('');
+      return;
+    }
+    // TODO: This should be the URL of the parent frame, not the tab. But
+    // chrome-extension:-URLs are not visible in the webNavigation API
+    // (https://crbug.com/326768), so the next best thing is using the tab's URL
+    // for making security decisions.
+    var parentUrl = sender.tab.url;
+    if (!parentUrl) {
+      sendResponse('');
+      return;
+    }
+    if (parentUrl.lastIndexOf('file:', 0) === 0) {
+      sendResponse('file://');
+      return;
+    }
+    // The regexp should always match for valid URLs, but in case it doesn't,
+    // just give the full URL (e.g. data URLs).
+    var origin = /^[^:]+:\/\/[^/]+/.exec(parentUrl);
+    sendResponse(origin ? origin[1] : parentUrl);
+    return true;
+  }
   if (message && message.action === 'isAllowedFileSchemeAccess') {
     chrome.extension.isAllowedFileSchemeAccess(sendResponse);
     return true;
diff --git a/web/chromecom.js b/web/chromecom.js
index 2b136fc65..8d4014084 100644
--- a/web/chromecom.js
+++ b/web/chromecom.js
@@ -113,18 +113,25 @@ var ChromeCom = (function ChromeComClosure() {
         return;
       }
       if (/^file?:/.test(file)) {
-        if (top !== window && !/^file:/i.test(location.ancestorOrigins[0])) {
-          PDFViewerApplication.error('Blocked ' + location.ancestorOrigins[0] +
-              ' from loading ' + file + '. Refused to load a local file in a ' +
-              ' non-local page for security reasons.');
-          return;
-        }
-        isAllowedFileSchemeAccess(function(isAllowedAccess) {
-          if (isAllowedAccess) {
-            PDFViewerApplication.open(file);
-          } else {
-            requestAccessToLocalFile(file);
+        getEmbedderOrigin(function(origin) {
+          // If the origin cannot be determined, let Chrome decide whether to
+          // allow embedding files. Otherwise, only allow local files to be
+          // embedded from local files or Chrome extensions.
+          // Even without this check, the file load in frames is still blocked,
+          // but this may change in the future (https://crbug.com/550151).
+          if (origin && !/^file:|^chrome-extension:/.test(origin)) {
+            PDFViewerApplication.error('Blocked ' + origin + ' from loading ' +
+                file + '. Refused to load a local file in a non-local page ' +
+                'for security reasons.');
+            return;
           }
+          isAllowedFileSchemeAccess(function(isAllowedAccess) {
+            if (isAllowedAccess) {
+              PDFViewerApplication.open(file);
+            } else {
+              requestAccessToLocalFile(file);
+            }
+          });
         });
         return;
       }
@@ -132,6 +139,20 @@ var ChromeCom = (function ChromeComClosure() {
     });
   };
 
+  function getEmbedderOrigin(callback) {
+    var origin = window === top ? location.origin : location.ancestorOrigins[0];
+    if (origin === 'null') {
+      // file:-URLs, data-URLs, sandboxed frames, etc.
+      getParentOrigin(callback);
+    } else {
+      callback(origin);
+    }
+  }
+
+  function getParentOrigin(callback) {
+    ChromeCom.request('getParentOrigin', null, callback);
+  }
+
   function isAllowedFileSchemeAccess(callback) {
     ChromeCom.request('isAllowedFileSchemeAccess', null, callback);
   }