Reland of Improve linearized pdf load/show time.

Original issue's description:
> Improve linearized pdf load/show time.
> Reduce Pdf Plugin's count of reconnects.
> Add tests for PDFPlugin DocumentLoader.
>
> DocumentLoader was splitted into separate components, and missing tests was added for them.
>
> The main ideas in this CL are:
>
> 1) Do not reset browser initiated connection at start (includes case when we can use range requests), if we request data near current downloading position.
> 2) Request as much data as we can on each request, and continue loading data using current range request. (like tape rewind)
> 3) Isolate RangeRequest logic into DocumentLoader.  Method OnPendingRequestComplete is called, when we receive requested data (main connection, or Range connection). (like tape playing without rewing).
> 4) Fill this logic by tests.
>
> Example URL:
> http://www.major-landrover.ru/upload/attachments/f/9/f96aab07dab04ae89c8a509ec1ef2b31.pdf
> Comparison of changes:
> https://drive.google.com/file/d/0BzWfMBOuik2QNGg0SG93Y3lpUlE/view?usp=sharing
>
> Committed: https://crrev.com/7fd7423cdee0dba84faf480d10dd66dcb57110d9
> Cr-Commit-Position: refs/heads/master@{#427752}

Original review:
https://codereview.chromium.org/2349753003/

Review-Url: https://codereview.chromium.org/2455403002
Cr-Commit-Position: refs/heads/master@{#429514}

pdf/BUILD.gn

@@ -18,10 +18,10 @@ static_library("pdf") {
     "//ppapi/cpp:objects",
     "//ppapi/cpp/private:internal_module",
     "//ui/base",
+    "//ui/gfx/range",
   ]
 
   sources = [
-    "chunk_stream.cc",
     "chunk_stream.h",
     "document_loader.cc",
     "document_loader.h",
@@ -38,6 +38,13 @@ static_library("pdf") {
     "pdf_engine.h",
     "preview_mode_client.cc",
     "preview_mode_client.h",
+    "range_set.cc",
+    "range_set.h",
+    "timer.cc",
+    "timer.h",
+    "url_loader_wrapper.h",
+    "url_loader_wrapper_impl.cc",
+    "url_loader_wrapper_impl.h",
   ]
 
   if (pdf_engine == 0) {
@@ -72,6 +79,8 @@ static_library("pdf") {
 test("pdf_unittests") {
   sources = [
     "chunk_stream_unittest.cc",
+    "document_loader_unittest.cc",
+    "range_set_unittest.cc",
     "run_all_unittests.cc",
   ]
 
@@ -83,5 +92,6 @@ test("pdf_unittests") {
     "//ppapi/cpp",
     "//testing/gmock",
     "//testing/gtest",
+    "//ui/gfx/range",
   ]
 }

pdf/DEPS

@@ -4,5 +4,6 @@ include_rules = [
   "+ppapi",
   "+ui/base/window_open_disposition.h",
   "+ui/events/keycodes/keyboard_codes.h",
+  "+ui/gfx/range/range.h",
   "+v8/include/v8.h"
 ]

pdf/chunk_stream.h

@@ -6,46 +6,103 @@
 #define PDF_CHUNK_STREAM_H_
 
 #include <stddef.h>
+#include <string.h>
 
-#include <map>
-#include <utility>
+#include <algorithm>
+#include <array>
+#include <memory>
 #include <vector>
 
+#include "pdf/range_set.h"
+
 namespace chrome_pdf {
 
 // This class collects a chunks of data into one data stream. Client can check
 // if data in certain range is available, and get missing chunks of data.
+template <uint32_t N>
 class ChunkStream {
  public:
-  ChunkStream();
-  ~ChunkStream();
+  static constexpr uint32_t kChunkSize = N;
+  using ChunkData = typename std::array<unsigned char, N>;
 
-  void Clear();
+  ChunkStream() {}
+  ~ChunkStream() {}
 
-  void Preallocate(size_t stream_size);
-  size_t GetSize() const;
+  void SetChunkData(uint32_t chunk_index, std::unique_ptr<ChunkData> data) {
+    if (!data)
+      return;
+    if (chunk_index >= data_.size()) {
+      data_.resize(chunk_index + 1);
+    }
+    if (!data_[chunk_index]) {
+      ++filled_chunks_count_;
+    }
+    data_[chunk_index] = std::move(data);
+    filled_chunks_.Union(gfx::Range(chunk_index, chunk_index + 1));
+  }
 
-  bool WriteData(size_t offset, void* buffer, size_t size);
-  bool ReadData(size_t offset, size_t size, void* buffer) const;
+  bool ReadData(const gfx::Range& range, void* buffer) const {
+    if (!IsRangeAvailable(range)) {
+      return false;
+    }
+    unsigned char* data_buffer = static_cast<unsigned char*>(buffer);
+    uint32_t start = range.start();
+    while (start != range.end()) {
+      const uint32_t chunk_index = GetChunkIndex(start);
+      const uint32_t chunk_start = start % kChunkSize;
+      const uint32_t len =
+          std::min(kChunkSize - chunk_start, range.end() - start);
+      memcpy(data_buffer, data_[chunk_index]->data() + chunk_start, len);
+      data_buffer += len;
+      start += len;
+    }
+    return true;
+  }
 
-  // Returns vector of pairs where first is an offset, second is a size.
-  bool GetMissedRanges(size_t offset, size_t size,
-      std::vector<std::pair<size_t, size_t> >* ranges) const;
-  bool IsRangeAvailable(size_t offset, size_t size) const;
-  size_t GetFirstMissingByte() const;
+  uint32_t GetChunkIndex(uint32_t offset) const { return offset / kChunkSize; }
 
-  // Finds the first byte of the missing byte interval that offset belongs to.
-  size_t GetFirstMissingByteInInterval(size_t offset) const;
-  // Returns the last byte of the missing byte interval that offset belongs to.
-  size_t GetLastMissingByteInInterval(size_t offset) const;
+  gfx::Range GetChunksRange(uint32_t offset, uint32_t size) const {
+    return gfx::Range(GetChunkIndex(offset),
+                      GetChunkIndex(offset + size + kChunkSize - 1));
+  }
 
- private:
-  std::vector<unsigned char> data_;
+  bool IsRangeAvailable(const gfx::Range& range) const {
+    if (!range.IsValid() || range.is_reversed() ||
+        (eof_pos_ > 0 && eof_pos_ < range.end()))
+      return false;
+    if (range.is_empty())
+      return true;
+    const gfx::Range chunks_range(GetChunkIndex(range.start()),
+                                  GetChunkIndex(range.end() + kChunkSize - 1));
+    return filled_chunks_.Contains(chunks_range);
+  }
+
+  void set_eof_pos(uint32_t eof_pos) { eof_pos_ = eof_pos; }
+  uint32_t eof_pos() const { return eof_pos_; }
+
+  const RangeSet& filled_chunks() const { return filled_chunks_; }
 
-  // Pair, first - begining of the chunk, second - size of the chunk.
-  std::map<size_t, size_t> chunks_;
+  bool IsComplete() const {
+    return eof_pos_ > 0 && IsRangeAvailable(gfx::Range(0, eof_pos_));
+  }
 
-  size_t stream_size_;
+  void Clear() {
+    data_.clear();
+    eof_pos_ = 0;
+    filled_chunks_.Clear();
+    filled_chunks_count_ = 0;
+  }
+
+  uint32_t filled_chunks_count() const { return filled_chunks_count_; }
+  uint32_t total_chunks_count() const {
+    return GetChunkIndex(eof_pos_ + kChunkSize - 1);
+  }
+
+ private:
+  std::vector<std::unique_ptr<ChunkData>> data_;
+  uint32_t eof_pos_ = 0;
+  RangeSet filled_chunks_;
+  uint32_t filled_chunks_count_ = 0;
 };
 
 };  // namespace chrome_pdf