Revert "Check file mime type provided by ARC before appending a file extension."

This reverts commit 1e471d39.

Reason for revert:
ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension is failling on Linux Chromium OS Asan Lsan Tests:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/28834
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/28835

[ RUN      ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:273: Failure
Expected equality of these values:
  "application/msword"
    Which is: 0x2de8e960
  FindArcMimeTypeFromExtension("doc")
    Which is: 0x2eaa2520
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:276: Failure
Expected equality of these values:
  "video/3gpp"
    Which is: 0x2de8e520
  FindArcMimeTypeFromExtension("3gp")
    Which is: 0x2eaa3aa0
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:279: Failure
Expected equality of these values:
  "audio/mpeg"
    Which is: 0x2de8eb60
  FindArcMimeTypeFromExtension("mpga")
    Which is: 0x2eaa2d60
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
[  FAILED  ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension (1 ms)
[ RUN      ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:273: Failure
Expected equality of these values:
  "application/msword"
    Which is: 0x2de8e960
  FindArcMimeTypeFromExtension("doc")
    Which is: 0x2eaa2520
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:276: Failure
Expected equality of these values:
  "video/3gpp"
    Which is: 0x2de8e520
  FindArcMimeTypeFromExtension("3gp")
    Which is: 0x2eaa3aa0
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:279: Failure
Expected equality of these values:
  "audio/mpeg"
    Which is: 0x2de8eb60
  FindArcMimeTypeFromExtension("mpga")
    Which is: 0x2eaa2d60
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
[  FAILED  ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension (2 ms)
[ RUN      ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:273: Failure
Expected equality of these values:
  "application/msword"
    Which is: 0x2de8e960
  FindArcMimeTypeFromExtension("doc")
    Which is: 0x2eaa2520
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:276: Failure
Expected equality of these values:
  "video/3gpp"
    Which is: 0x2de8e520
  FindArcMimeTypeFromExtension("3gp")
    Which is: 0x2eaa3aa0
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:279: Failure
Expected equality of these values:
  "audio/mpeg"
    Which is: 0x2de8eb60
  FindArcMimeTypeFromExtension("mpga")
    Which is: 0x2eaa2d60
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
[  FAILED  ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension (1 ms)
[ RUN      ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:273: Failure
Expected equality of these values:
  "application/msword"
    Which is: 0x2de8e960
  FindArcMimeTypeFromExtension("doc")
    Which is: 0x2eaa2520
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:276: Failure
Expected equality of these values:
  "video/3gpp"
    Which is: 0x2de8e520
  FindArcMimeTypeFromExtension("3gp")
    Which is: 0x2eaa3aa0
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc:279: Failure
Expected equality of these values:
  "audio/mpeg"
    Which is: 0x2de8eb60
  FindArcMimeTypeFromExtension("mpga")
    Which is: 0x2eaa2d60
Stack trace:
#0 0x000008bf16ff (/b/s/w/ir/out/Release/unit_tests+0x8bf16fe)
#1 0x000008c17af0 (/b/s/w/ir/out/Release/unit_tests+0x8c17aef)
#2 0x000008c166ca (/b/s/w/ir/out/Release/unit_tests+0x8c166c9)
[  FAILED  ] ArcDocumentsProviderUtilTest.FindArcMimeTypeFromExtension (2 ms)

Original change's description:
> Check file mime type provided by ARC before appending a file extension.
> 
> Some files are returned with an unexpected mime type (eg. 3gp and video/mp4) causing an extra
> extension to be appended when it is not in the list of allowed extensions returned by
> net::GetExtensionsForMimeType. In those cases, do an extra lookup in the Android mapping by
> extension, and don't append the extension if a valid MIME type is returned and the MIME
> category type (ie. MIME type without the subtype) matches.
> 
> Bug: 844252
> Test: Tested on kevin.
> Change-Id: I9899d74d6046d6c392adc4f828af09296c73f1c6
> Reviewed-on: https://chromium-review.googlesource.com/1189690
> Commit-Queue: Alex Lau <alexlau@chromium.org>
> Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
> Reviewed-by: Shuhei Takahashi <nya@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#588444}

TBR=hidehiko@chromium.org,nya@chromium.org,alexlau@chromium.org

Change-Id: I6b77806153d942e9f996624a2d782448371c04bb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 844252
Reviewed-on: https://chromium-review.googlesource.com/1203353Reviewed-by: Takashi Sakamoto <tasak@google.com>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/master@{#588463}

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util.cc

@@ -217,30 +217,6 @@ std::vector<base::FilePath::StringType> GetExtensionsForArcMimeType(
   return std::vector<base::FilePath::StringType>();
 }
 
-std::string StripMimeSubType(const std::string& mime_type) {
-  if (mime_type.empty())
-    return mime_type;
-  size_t index = mime_type.find_first_of('/', 0);
-  if (index == 0 || index == mime_type.size() - 1 ||
-      index == std::string::npos) {
-    // This looks malformed, return an empty string.
-    return std::string();
-  }
-  return mime_type.substr(0, index);
-}
-
-// This is based on net/base/mime_util.cc: net::FindMimeType.
-const char* FindArcMimeTypeFromExtension(const std::string& ext) {
-  for (const auto& mapping : kAndroidMimeTypeMappings) {
-    std::vector<base::StringPiece> extensions = base::SplitStringPiece(
-        mapping.extensions, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
-    auto iter = std::find(extensions.begin(), extensions.end(), ext);
-    if (iter != extensions.end())
-      return mapping.mime_type;
-  }
-  return nullptr;
-}
-
 // TODO(crbug.com/675868): Consolidate with the similar logic for Drive.
 base::FilePath::StringType GetFileNameForDocument(
     const mojom::DocumentPtr& document) {
@@ -267,23 +243,10 @@ base::FilePath::StringType GetFileNameForDocument(
     extension = extension.substr(1);  // Strip the leading dot.
   std::vector<base::FilePath::StringType> possible_extensions =
       GetExtensionsForArcMimeType(document->mime_type);
-
   if (!possible_extensions.empty() &&
       !base::ContainsValue(possible_extensions, extension)) {
-    // Lookup the extension in the hardcoded map before appending an extension,
-    // as some extensions (eg. 3gp) are typed differently by Android. Only
-    // append the suggested extension if the lookup fails (i.e. no valid mime
-    // type returned), or the returned mime type is of a different category.
-    // TODO(crbug.com/878221): Fix discrepancy in MIME types and extensions
-    // between the hard coded map and the Android content provider.
-    const char* missed_possible_mime_type =
-        FindArcMimeTypeFromExtension(extension);
-    if (missed_possible_mime_type == nullptr ||
-        StripMimeSubType(document->mime_type) !=
-            StripMimeSubType(missed_possible_mime_type)) {
-      filename =
-          base::FilePath(filename).AddExtension(possible_extensions[0]).value();
-    }
+    filename =
+        base::FilePath(filename).AddExtension(possible_extensions[0]).value();
   }
 
   return filename;

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util.h

@@ -75,14 +75,6 @@ std::vector<base::FilePath::StringType> GetExtensionsForArcMimeType(
 base::FilePath::StringType GetFileNameForDocument(
     const mojom::DocumentPtr& document);
 
-// Returns the provided MIME type without the subtype component.
-std::string StripMimeSubType(const std::string& mime_type);
-
-// Finds the first matching mime type with |ext| as a valid extension from the
-// internal list of Android mime types. On success, the first matching MIME type
-// is returned. On failure, nullptr is returned.
-const char* FindArcMimeTypeFromExtension(const std::string& ext);
-
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_DOCUMENTS_PROVIDER_UTIL_H_

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util_unittest.cc

@@ -243,49 +243,6 @@ TEST(ArcDocumentsProviderUtilTest, GetFileNameForDocument) {
             GetFileNameForDocument(MakeDocument("kitten", "image/png")));
   EXPECT_EQ("kitten",
             GetFileNameForDocument(MakeDocument("kitten", "abc/xyz")));
-
-  // Check that files with a mime type different than expected appends a
-  // possible extension when a different mime type with a different category is
-  // found in the Android mime types map.
-  EXPECT_EQ("file.txt.3gp",
-            GetFileNameForDocument(MakeDocument("file.txt", "video/3gpp")));
-
-  // Check that files with a mime type different than expected don't append
-  // an extension when a different mime type with the same category is
-  // found in the Android mime types map.
-  EXPECT_EQ("file.3gp",
-            GetFileNameForDocument(MakeDocument("file.3gp", "video/mp4")));
-}
-
-TEST(ArcDocumentsProviderUtilTest, StripMimeSubType) {
-  // Check that the category type is returned for a valid mime type.
-  EXPECT_EQ("video", StripMimeSubType("video/mp4"));
-  // Check that an empty string is returned for malformed mime types.
-  EXPECT_EQ("", StripMimeSubType(""));
-  EXPECT_EQ("", StripMimeSubType("video/"));
-  EXPECT_EQ("", StripMimeSubType("/"));
-  EXPECT_EQ("", StripMimeSubType("/abc"));
-  EXPECT_EQ("", StripMimeSubType("/abc/xyz"));
-}
-
-TEST(ArcDocumentsProviderUtilTest, FindArcMimeTypeFromExtension) {
-  // Test that a lone possible extension returns the correct type.
-  EXPECT_EQ("application/msword", FindArcMimeTypeFromExtension("doc"));
-  // Test that the first extension in the comma delimited list of extensions
-  // returns the correct type.
-  EXPECT_EQ("video/3gpp", FindArcMimeTypeFromExtension("3gp"));
-  // Test that the second extension in the comma delimited list of extensions
-  // returns the correct type.
-  EXPECT_EQ("audio/mpeg", FindArcMimeTypeFromExtension("mpga"));
-  // Test that matching suffixes (m4a) return null without a full match.
-  EXPECT_EQ(nullptr, FindArcMimeTypeFromExtension("4a"));
-  // Test that matching prefixes (imy) return null without a full match.
-  EXPECT_EQ(nullptr, FindArcMimeTypeFromExtension("im"));
-  // Test that ambiguous prefixes (mp4, mpg) return null.
-  EXPECT_EQ(nullptr, FindArcMimeTypeFromExtension("mp"));
-  // Test that invalid mime types return null.
-  EXPECT_EQ(nullptr, FindArcMimeTypeFromExtension(""));
-  EXPECT_EQ(nullptr, FindArcMimeTypeFromExtension("invalid"));
 }
 
 }  // namespace