Photo Picker Dialog: Recursively traverse the photo directories.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/MimeTypeFileFilter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/photo_picker/MimeTypeFileFilter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/MimeTypeFileFilter.java b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/MimeTypeFileFilter.java
new file mode 100644
index 0000000000000000000000000000000000000000..2b64157e436711fa8bc78bf667f160887115a10a
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/MimeTypeFileFilter.java
@@ -0,0 +1,94 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.photo_picker;
+
+import android.support.annotation.NonNull;
+import android.webkit.MimeTypeMap;
+
+import java.io.File;
+import java.io.FileFilter;
+import java.util.HashSet;
+import java.util.Locale;
+
+/**
+ * A file filter for handling extensions mapping to MIME types (such as images/jpeg and images/*).
+ */
+class MimeTypeFileFilter implements FileFilter {
+    private HashSet<String> mExtensions = new HashSet<>();
+    private HashSet<String> mMimeTypes = new HashSet<>();
+    private HashSet<String> mMimeSupertypes = new HashSet<>();
+    private MimeTypeMap mMimeTypeMap;
+
+    /**
+     * Contructs a MimeTypeFileFilter object.
+     * @param acceptAttr A comma seperated list of MIME types this filter accepts.
+     *                   For example: images/gif, video/*.
+     */
+    // TODO(finnur): Convert param to List.
+    public MimeTypeFileFilter(@NonNull String acceptAttr) {
+        for (String field : acceptAttr.toLowerCase(Locale.US).split(",")) {
+            field = field.trim();
+            if (field.startsWith(".")) {
+                mExtensions.add(field.substring(1));
+            } else if (field.endsWith("/*")) {
+                mMimeSupertypes.add(field.substring(0, field.length() - 2));
+            } else if (field.contains("/")) {
+                mMimeTypes.add(field);
+            } else {
+                // Throw exception?
+            }
+        }
+
+        mMimeTypeMap = MimeTypeMap.getSingleton();
+    }
+
+    @Override
+    public boolean accept(@NonNull File file) {
+        if (file.isDirectory()) {
+            return true;
+        }
+
+        String uri = file.toURI().toString();
+        String ext = MimeTypeMap.getFileExtensionFromUrl(uri).toLowerCase(Locale.US);
+        if (mExtensions.contains(ext)) {
+            return true;
+        }
+
+        String mimeType = getMimeTypeFromExtension(ext);
+        if (mimeType != null) {
+            if (mMimeTypes.contains(mimeType)
+                    || mMimeSupertypes.contains(getMimeSupertype(mimeType))) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private HashSet<String> getAcceptedSupertypes() {
+        HashSet<String> supertypes = new HashSet<>();
+        supertypes.addAll(mMimeSupertypes);
+        for (String mimeType : mMimeTypes) {
+            supertypes.add(getMimeSupertype(mimeType));
+        }
+        for (String ext : mExtensions) {
+            String mimeType = getMimeTypeFromExtension(ext);
+            if (mimeType != null) {
+                supertypes.add(getMimeSupertype(mimeType));
+            }
+        }
+        return supertypes;
+    }
+
+    private String getMimeTypeFromExtension(@NonNull String ext) {
+        String mimeType = mMimeTypeMap.getMimeTypeFromExtension(ext);
+        return (mimeType != null) ? mimeType.toLowerCase(Locale.US) : null;
+    }
+
+    @NonNull
+    private String getMimeSupertype(@NonNull String mimeType) {
+        return mimeType.split("/", 2)[0];
+    }
+}