SymbolVendor: Move compile unit handling into the SymbolFile class

Summary:
SymbolFile classes are responsible for creating CompileUnit instances
and they already need to have a notion of the id<->CompileUnit mapping
(because of APIs like ParseCompileUnitAtIndex). However, the
SymbolVendor has remained as the thing responsible for caching created
units (which the SymbolFiles were calling via convoluted constructs like
"m_obj_file->GetModule()->GetSymbolVendor()->SetCompileUnitAtIndex(...)").

This patch moves the responsibility of caching the units into the
SymbolFile class. It does this by moving the implementation of
SymbolVendor::{GetNumCompileUnits,GetCompileUnitAtIndex} into the
equivalent SymbolFile functions. The SymbolVendor functions become just
a passthrough much like the rest of SymbolVendor.

The original implementations of SymbolFile::GetNumCompileUnits is moved
to "CalculateNumCompileUnits", and are made protected, as the "Get"
function is the external api of the class.
SymbolFile::ParseCompileUnitAtIndex is made protected for the same
reason.

This is the first step in removing the SymbolVendor indirection, as
proposed in
<http://lists.llvm.org/pipermail/lldb-dev/2019-June/015071.html>. After
removing all interesting logic from the SymbolVendor class, I'll proceed
with removing the indirection itself.

Reviewers: clayborg, jingham, JDevlieghere

Subscribers: jdoerfert, lldb-commits

Differential Revision: https://reviews.llvm.org/D65089

llvm-svn: 366791
diff --git a/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h b/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h
index 8a0b764..6803636 100644
--- a/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h
+++ b/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h
@@ -46,10 +46,6 @@
 
   // Compile Unit function calls
 
-  uint32_t GetNumCompileUnits() override;
-
-  lldb::CompUnitSP ParseCompileUnitAtIndex(uint32_t index) override;
-
   lldb::LanguageType ParseLanguage(CompileUnit &comp_unit) override {
     return lldb::eLanguageTypeUnknown;
   }
@@ -196,7 +192,9 @@
 
   };
 
-  SymbolVendor &GetSymbolVendor();
+  uint32_t CalculateNumCompileUnits() override;
+  lldb::CompUnitSP ParseCompileUnitAtIndex(uint32_t index) override;
+
   lldb::addr_t GetBaseFileAddress();
   void ParseFileRecords();
   void ParseCUData();