Postpone MaxSharedFileBytes check

Removing the check of the size of the shared files from
share_service_impl, but leaving the unit tests prepped to cover these
cases to validate that the platform-specific implementations check this
when they are processing the shared files.

The scenario being fixed with this change is sharing native files,
easily exercised with the Web Share Test page:
https://w3c.github.io/web-share/demos/share-files.html

When these files are initially created as blobs they are marked as being
of unknown size, and though the navigator_share code does check their
size as part of the Share operation, this check does not modify the
actual blob, so when it is serialized the recorded size will be the max
uint64 value. Matching the Android implementation, this postpones the
file size check till the files are actually being processed (in the
platform-specific implementations).

Bug: 1035527
Change-Id: I59ea9bfadb06205ae155f31947fa04093f06503d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2415431Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: Hoch Hochkeppel <mhochk@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#807765}

chrome/browser/webshare/share_service_impl.cc

@@ -133,7 +133,6 @@ void ShareServiceImpl::Share(const std::string& title,
     return;
   }
 
-  uint64_t total_bytes = 0;
   for (auto& file : files) {
     if (!file || !file->blob) {
       mojo::ReportBadMessage("Invalid file to share()");
@@ -146,12 +145,11 @@ void ShareServiceImpl::Share(const std::string& title,
       return;
     }
 
-    total_bytes += file->blob->size;
-  }
-
-  if (total_bytes > kMaxSharedFileBytes) {
-    std::move(callback).Run(blink::mojom::ShareError::PERMISSION_DENIED);
-    return;
+    // In the case where the original blob handle was to a native file (of
+    // unknown size), the serialized data does not contain an accurate file
+    // size. To handle this, the comparison against kMaxSharedFileBytes should
+    // be done by the platform-specific implementations as part of processing
+    // the blobs.
   }
 
   // TODO(crbug.com/1035527): Add implementation for OS_WIN

chrome/browser/webshare/share_service_unittest.cc

@@ -79,7 +79,7 @@ TEST_F(ShareServiceUnitTest, TotalBytes) {
                                    kMaxSharedFileBytes / kMaxSharedFileCount,
                                    kMaxSharedFileCount));
   EXPECT_EQ(
-      ShareError::PERMISSION_DENIED,
+      ShareError::CANCELED,
       ShareGeneratedFileData(".txt", "text/plain",
                              (kMaxSharedFileBytes / kMaxSharedFileCount) + 1,
                              kMaxSharedFileCount));
@@ -89,7 +89,7 @@ TEST_F(ShareServiceUnitTest, FileBytes) {
   EXPECT_EQ(ShareError::CANCELED,
             ShareGeneratedFileData(".txt", "text/plain", kMaxSharedFileBytes));
   EXPECT_EQ(
-      ShareError::PERMISSION_DENIED,
+      ShareError::CANCELED,
       ShareGeneratedFileData(".txt", "text/plain", kMaxSharedFileBytes + 1));
 }