Content verification: Don't fail on non-existence.

This prevents content verification (when active) from disabling
an extension when the extension attempts to load a non-existent
resource in its own chrome-extension URL space.

BUG=404802

Review URL: https://codereview.chromium.org/512573003

Cr-Commit-Position: refs/heads/master@{#292095}

extensions/browser/content_hash_reader.cc

@@ -35,6 +35,7 @@ ContentHashReader::ContentHashReader(const std::string& extension_id,
       relative_path_(relative_path),
       key_(key),
       status_(NOT_INITIALIZED),
+      content_exists_(false),
       have_verified_contents_(false),
       have_computed_hashes_(false),
       block_size_(0) {
@@ -50,6 +51,13 @@ bool ContentHashReader::Init() {
   base::FilePath verified_contents_path =
       file_util::GetVerifiedContentsPath(extension_root_);
 
+  // Check that this is a valid resource to verify (i.e., it exists).
+  base::FilePath content_path = extension_root_.Append(relative_path_);
+  if (!base::PathExists(content_path))
+    return false;
+
+  content_exists_ = true;
+
   if (!base::PathExists(verified_contents_path))
     return false;
 

extensions/browser/content_hash_reader.h

@@ -40,11 +40,15 @@ class ContentHashReader : public base::RefCountedThreadSafe<ContentHashReader> {
   // should likely be discarded.
   bool Init();
 
+  // Indicates whether the content in question exists in the local extension
+  // installation. This may be |false| if Init fails.
+  bool content_exists() const { return content_exists_; }
+
   // These return whether we found valid verified_contents.json /
   // computed_hashes.json files respectively. Note that both of these can be
   // true but we still didn't find an entry for |relative_path_| in them.
-  bool have_verified_contents() { return have_verified_contents_; }
-  bool have_computed_hashes() { return have_computed_hashes_; }
+  bool have_verified_contents() const { return have_verified_contents_; }
+  bool have_computed_hashes() const { return have_computed_hashes_; }
 
   // Return the number of blocks and block size, respectively. Only valid after
   // calling Init().
@@ -69,6 +73,8 @@ class ContentHashReader : public base::RefCountedThreadSafe<ContentHashReader> {
 
   InitStatus status_;
 
+  bool content_exists_;
+
   bool have_verified_contents_;
   bool have_computed_hashes_;
 

extensions/browser/content_verify_job.cc

@@ -152,11 +152,15 @@ bool ContentVerifyJob::FinishBlock() {
 
 void ContentVerifyJob::OnHashesReady(bool success) {
   if (!success && !g_test_delegate) {
-    if (hash_reader_->have_verified_contents() &&
-        hash_reader_->have_computed_hashes())
+    if (!hash_reader_->content_exists()) {
+      // Ignore verification of non-existent resources.
+      return;
+    } else if (hash_reader_->have_verified_contents() &&
+               hash_reader_->have_computed_hashes()) {
       DispatchFailureCallback(NO_HASHES_FOR_FILE);
-    else
+    } else {
       DispatchFailureCallback(MISSING_ALL_HASHES);
+    }
     return;
   }